diff --git a/libsrc/core/CMakeLists.txt b/libsrc/core/CMakeLists.txt
index 8b14b211..332740bb 100644
--- a/libsrc/core/CMakeLists.txt
+++ b/libsrc/core/CMakeLists.txt
@@ -5,6 +5,6 @@ set_target_properties(ngcore PROPERTIES POSITION_INDEPENDENT_CODE ON )
 
 install(TARGETS ngcore DESTINATION ${NG_INSTALL_DIR} COMPONENT netgen)
 
-install(FILES ngcore.hpp archive.hpp basearchive.hpp
+install(FILES ngcore.hpp archive.hpp basearchive.hpp version.hpp
   DESTINATION ${NG_INSTALL_DIR_INCLUDE}/core COMPONENT netgen_devel
 )
diff --git a/libsrc/core/archive.hpp b/libsrc/core/archive.hpp
index 7b213b8d..7da24f98 100644
--- a/libsrc/core/archive.hpp
+++ b/libsrc/core/archive.hpp
@@ -6,16 +6,22 @@ namespace ngcore
   // BinaryOutArchive ======================================================================
   class BinaryOutArchive : public Archive
   {
-    std::shared_ptr<std::ostream> fout;
     size_t ptr = 0;
     enum { BUFFERSIZE = 1024 };
     char buffer[BUFFERSIZE];
+    std::shared_ptr<std::ostream> fout;
   public:
-    BinaryOutArchive (std::shared_ptr<std::ostream> afout) : Archive(true), fout(afout) { ; }
-    BinaryOutArchive (std::string filename)
+    BinaryOutArchive(std::shared_ptr<std::ostream> afout) : Archive(true), fout(afout)
+    {
+      (*this) & GetLibraryVersions();
+    }
+    BinaryOutArchive(std::string filename)
       : BinaryOutArchive(std::make_shared<std::ofstream>(filename)) {}
     virtual ~BinaryOutArchive () { FlushBuffer(); }
 
+    const VersionInfo& getVersion(const std::string& library)
+    { return GetLibraryVersions()[library]; }
+
     using Archive::operator&;
     virtual Archive & operator & (double & d)
     { return Write(d); }
@@ -76,11 +82,18 @@ namespace ngcore
   // BinaryInArchive ======================================================================
   class BinaryInArchive : public Archive
   {
+    std::map<std::string, VersionInfo> vinfo;
     std::shared_ptr<std::istream> fin;
   public:
-    BinaryInArchive (std::shared_ptr<std::istream> afin) : Archive(false), fin(afin) { ; }
+    BinaryInArchive (std::shared_ptr<std::istream> afin) : Archive(false), fin(afin)
+    {
+      (*this) & vinfo;
+    }
     BinaryInArchive (std::string filename)
-      : BinaryInArchive(std::make_shared<std::ifstream>(filename)) {}
+      : BinaryInArchive(std::make_shared<std::ifstream>(filename)) { ; }
+
+    const VersionInfo& getVersion(const std::string& library)
+    { return vinfo[library]; }
 
     using Archive::operator&;
     virtual Archive & operator & (double & d)
@@ -133,10 +146,16 @@ namespace ngcore
   {
     std::shared_ptr<std::ostream> fout;
   public:
-    TextOutArchive (std::shared_ptr<std::ostream> afout) : Archive(true), fout(afout) { }
+    TextOutArchive (std::shared_ptr<std::ostream> afout) : Archive(true), fout(afout)
+    {
+      (*this) & GetLibraryVersions();
+    }
     TextOutArchive (std::string filename) :
       TextOutArchive(std::make_shared<std::ofstream>(filename.c_str())) { }
 
+    const VersionInfo& getVersion(const std::string& library)
+    { return GetLibraryVersions()[library]; }
+
     using Archive::operator&;
     virtual Archive & operator & (double & d)
     { *fout << d << '\n'; return *this; }
@@ -156,16 +175,22 @@ namespace ngcore
     {
       int len = str.length();
       *fout << len << '\n';
-      fout->write(&str[0], len);
-      *fout << '\n';
+      if(len)
+        {
+          fout->write(&str[0], len);
+          *fout << '\n';
+        }
       return *this;
     }
     virtual Archive & operator & (char *& str)
     {
       int len = strlen (str);
       *fout << len << '\n';
-      fout->write (&str[0], len);
-      *fout << '\n';
+      if(len)
+        {
+          fout->write (&str[0], len);
+          *fout << '\n';
+        }
       return *this;
     }
   };
@@ -173,12 +198,19 @@ namespace ngcore
   // TextInArchive ======================================================================
   class TextInArchive : public Archive
   {
+    std::map<std::string, VersionInfo> vinfo;
     std::shared_ptr<std::istream> fin;
   public:
-    TextInArchive (std::shared_ptr<std::istream> afin) : Archive(false), fin(afin) { ; }
+    TextInArchive (std::shared_ptr<std::istream> afin) : Archive(false), fin(afin)
+    {
+      (*this) & vinfo;
+    }
     TextInArchive (std::string filename)
       : TextInArchive(std::make_shared<std::ifstream>(filename)) {}
 
+    const VersionInfo& getVersion(const std::string& library)
+    { return vinfo[library]; }
+
     using Archive::operator&;
     virtual Archive & operator & (double & d)
     { *fin >> d; return *this; }
@@ -201,7 +233,8 @@ namespace ngcore
       char ch;
       fin->get(ch); // '\n'
       str.resize(len);
-      fin->get(&str[0], len+1, '\0');
+      if(len)
+        fin->get(&str[0], len+1, '\0');
       return *this;
     }
     virtual Archive & operator & (char *& str)
@@ -211,7 +244,8 @@ namespace ngcore
       char ch;
       fin->get(ch); // '\n'
       str = new char[len+1];
-      fin->get(&str[0], len, '\0');
+      if(len)
+        fin->get(&str[0], len, '\0');
       str[len] = 0;
       return *this;
     }
diff --git a/libsrc/core/basearchive.cpp b/libsrc/core/basearchive.cpp
index 1fb0d713..975006fc 100644
--- a/libsrc/core/basearchive.cpp
+++ b/libsrc/core/basearchive.cpp
@@ -7,6 +7,11 @@
 
 namespace ngcore
 {
+  std::map<std::string, VersionInfo>& GetLibraryVersions()
+  {
+    static std::map<std::string, VersionInfo> library_versions;
+    return library_versions;
+  }
 #ifdef WIN
   // windows does demangling in typeid(T).name()
   std::string demangle(const char* typeinfo) { return typeinfo; }
diff --git a/libsrc/core/basearchive.hpp b/libsrc/core/basearchive.hpp
index 26ca217e..9fdf95e0 100644
--- a/libsrc/core/basearchive.hpp
+++ b/libsrc/core/basearchive.hpp
@@ -3,6 +3,10 @@
 
 namespace ngcore
 {
+  class VersionInfo;
+  // Libraries using this archive can store their version here to implement backwards compatibility
+  std::map<std::string, VersionInfo>& GetLibraryVersions();
+
   class Archive;
   std::string demangle(const char* typeinfo);
 
@@ -75,6 +79,7 @@ namespace ngcore
 
     bool Output () { return is_output; }
     bool Input () { return !is_output; }
+    virtual const VersionInfo& getVersion(const std::string& library) = 0;
 
     // Pure virtual functions that have to be implemented by In-/OutArchive
     virtual Archive & operator & (double & d) = 0;
@@ -116,6 +121,29 @@ namespace ngcore
       Do(&v[0], size);
       return (*this);
     }
+    template<typename T1, typename T2>
+    Archive& operator& (std::map<T1, T2>& map)
+    {
+      if(is_output)
+        {
+          (*this) << size_t(map.size());
+          for(auto& pair : map)
+              (*this) << pair.first << pair.second;
+        }
+      else
+        {
+          size_t size;
+          (*this) & size;
+          T1 key; T2 val;
+          for(size_t i = 0; i < size; i++)
+            {
+              T1 key; T2 val;
+              (*this) & key & val;
+              map[key] = val;
+            }
+        }
+      return (*this);
+    }
     // Archive arrays =====================================================
     // this functions can be overloaded in Archive implementations for more efficiency
     template <typename T>
diff --git a/libsrc/core/ngcore.hpp b/libsrc/core/ngcore.hpp
index e93a506c..0a37c977 100644
--- a/libsrc/core/ngcore.hpp
+++ b/libsrc/core/ngcore.hpp
@@ -6,6 +6,7 @@
 #include <string>
 #include <vector>
 #include <map>
+#include <iterator>
 #include <type_traits>
 #include <functional>
 #include <stdexcept>
@@ -15,6 +16,8 @@
 #include <complex>
 
 
+namespace ngcore
+{
 #if defined(__GNUC__)
   inline bool likely (bool x) { return __builtin_expect((x), true); }
   inline bool unlikely (bool x) { return __builtin_expect((x), false); }
@@ -22,9 +25,11 @@
   inline bool likely (bool x) { return x; }
   inline bool unlikely (bool x) { return x; }
 #endif
+}
 
 // own includes
 #include "basearchive.hpp"
+#include "version.hpp"
 #include "archive.hpp"
 
 #endif // NG_CORE_HPP
diff --git a/libsrc/core/version.hpp b/libsrc/core/version.hpp
new file mode 100644
index 00000000..bf11b3e9
--- /dev/null
+++ b/libsrc/core/version.hpp
@@ -0,0 +1,84 @@
+
+namespace ngcore
+{
+  class VersionInfo
+  {
+  private:
+    size_t mayor, minor, date, commit_offset;
+    std::string git_hash;
+  public:
+    VersionInfo() : mayor(0), minor(0), date(0), commit_offset(0), git_hash("") {}
+    VersionInfo(std::string vstring)
+    {
+      minor = date = commit_offset = 0;
+      git_hash = "";
+      if(vstring.substr(0,1) == "v")
+        vstring = vstring.substr(1,vstring.size()-1);
+      auto dot = vstring.find(".");
+      mayor = std::stoi(vstring.substr(0,dot));
+      if(dot == size_t(-1)) vstring = "";
+      else vstring = vstring.substr(dot+1, vstring.size()-dot-1);
+      if(vstring.size())
+        {
+          dot = vstring.find(".");
+          minor = std::stoi(vstring.substr(0,dot));
+          if (dot == size_t(-1)) vstring = "";
+          else vstring = vstring.substr(dot+1, vstring.size()-dot-1);
+          if(vstring.size())
+            {
+              dot = vstring.find("-");
+              date = std::stoi(vstring.substr(0,dot));
+              if(dot == size_t(-1)) vstring = "";
+              else vstring = vstring.substr(dot+1,vstring.size()-dot-1);
+              if(vstring.size())
+                {
+                  dot = vstring.find("-");
+                  commit_offset = std::stoi(vstring.substr(0,dot));
+                  if(dot == size_t(-1)) vstring = "";
+                  else vstring = vstring.substr(dot+1, vstring.size()-dot-1);
+                  if(vstring.size())
+                    git_hash = vstring;
+                }
+            }
+        }
+    }
+    VersionInfo(const char* cstr) : VersionInfo(std::string(cstr)) { }
+
+    std::string to_string() const
+    { std::string vstring = "v" + std::to_string(mayor);
+      if(minor || date || commit_offset || git_hash.size())
+        {
+          vstring += "." + std::to_string(minor);
+          if(date || commit_offset || git_hash.size())
+            {
+              vstring += "." + std::to_string(date);
+              if(commit_offset || git_hash.size())
+                {
+                  vstring += "-" + std::to_string(commit_offset);
+                  if(git_hash.size())
+                    vstring += "-" + git_hash;
+                }
+            }
+        }
+      return vstring;
+    }
+    bool operator <(const VersionInfo& other) const
+    {
+      return std::tie(mayor, minor, date, commit_offset) <
+        std::tie(other.mayor, other.minor, other.date, other.commit_offset);
+    }
+    bool operator ==(const VersionInfo& other) const
+    {
+      return mayor == other.mayor && minor == other.minor && date == other.date
+        && commit_offset == other.commit_offset;
+    }
+    bool operator >(const VersionInfo& other) const { return other < (*this); }
+    bool operator <=(const VersionInfo& other) const { return !((*this) > other); }
+    bool operator >=(const VersionInfo& other) const { return !((*this) < other); }
+
+    void DoArchive(Archive& ar)
+    {
+      ar & mayor & minor & date & commit_offset & git_hash;
+    }
+  };
+}
diff --git a/libsrc/csg/python_csg.cpp b/libsrc/csg/python_csg.cpp
index 05ac4acc..e9895738 100644
--- a/libsrc/csg/python_csg.cpp
+++ b/libsrc/csg/python_csg.cpp
@@ -371,19 +371,17 @@ However, when r = 0, the top part becomes a point(tip) and meshing fails!
     .def(py::pickle(
                     [](CSGeometry& self)
                     {
-                      stringstream ss;
-                      self.Save(ss);
-                      cout << "pickle = " << endl << ss.str() << endl;
-                      return py::make_tuple(ss.str());
+                      auto ss = make_shared<stringstream>();
+                      BinaryOutArchive archive(ss);
+                      archive & self;
+                      return py::make_tuple(ss->str());
                     },
                     [](py::tuple state)
                     {
                       auto geo = make_shared<CSGeometry>();
-                      auto val = py::cast<string>(state[0]);
-                      cout << "unpickle = " << endl << val << endl;
-                      stringstream ss(py::cast<string>(state[0]));
-                      // geo->Load(ss);
-                      // geo->FindIdenticSurfaces(1e-8 * geo->MaxSize());
+                      auto ss = make_shared<stringstream> (py::cast<string>(state[0]));
+                      BinaryInArchive archive(ss);
+                      archive & (*geo);
                       return geo;
                     }))
     .def("Save", FunctionPointer([] (CSGeometry & self, string filename)
diff --git a/tests/catch/CMakeLists.txt b/tests/catch/CMakeLists.txt
index d980d7f8..53cacdda 100644
--- a/tests/catch/CMakeLists.txt
+++ b/tests/catch/CMakeLists.txt
@@ -27,4 +27,5 @@ macro(add_unit_test name sources)
 endmacro()
 
 add_unit_test(archive archive.cpp)
+add_unit_test(version version.cpp)
 endif(ENABLE_UNIT_TESTS)
diff --git a/tests/catch/archive.cpp b/tests/catch/archive.cpp
index 40ee202b..f6fb4bc8 100644
--- a/tests/catch/archive.cpp
+++ b/tests/catch/archive.cpp
@@ -203,8 +203,24 @@ void testMultipleInheritance(Archive& in, Archive& out)
     }
 }
 
+void testLibraryVersion(Archive& in, Archive& out)
+{
+  GetLibraryVersions()["netgen"] = "v6.2.1812";
+  CHECK(in.getVersion("netgen") == "v6.2.1811");
+  CHECK(out.getVersion("netgen") == "v6.2.1812");
+}
+
 void testArchive(Archive& in, Archive& out)
 {
+  SECTION("Empty String")
+    {
+      out << string("") << 1;
+      out.FlushBuffer();
+      string str; int i;
+      in & str & i;
+      CHECK(str == "");
+      CHECK(i == 1);
+    }
   SECTION("SharedPtr")
     {
       testSharedPointer(in, out);
@@ -226,10 +242,15 @@ void testArchive(Archive& in, Archive& out)
     {
       testNullPtr(in, out);
     }
+  SECTION("Library Version")
+    {
+      testLibraryVersion(in,out);
+    }
 }
 
 TEST_CASE("BinaryArchive")
 {
+  GetLibraryVersions()["netgen"] = "v6.2.1811";
   auto stream = make_shared<stringstream>();
   BinaryOutArchive out(stream);
   BinaryInArchive in(stream);
@@ -238,6 +259,7 @@ TEST_CASE("BinaryArchive")
 
 TEST_CASE("TextArchive")
 {
+  GetLibraryVersions()["netgen"] = "v6.2.1811";
   auto stream = make_shared<stringstream>();
   TextOutArchive out(stream);
   TextInArchive in(stream);
diff --git a/tests/catch/version.cpp b/tests/catch/version.cpp
new file mode 100644
index 00000000..5655ab23
--- /dev/null
+++ b/tests/catch/version.cpp
@@ -0,0 +1,19 @@
+
+#include "catch.hpp"
+#include <../core/ngcore.hpp>
+using namespace ngcore;
+using namespace std;
+
+
+TEST_CASE("Version")
+{
+  VersionInfo v("v6.2.1811-3-asdf");
+  CHECK(v.to_string() == "v6.2.1811-3-asdf");
+  VersionInfo v2("6.2");
+  CHECK(v2.to_string() == "v6.2");
+  CHECK(v < "v7");
+  CHECK(v >= "6.2");
+  CHECK(v > "6.2.1811");
+  CHECK(v < "6.2.1811-5");
+  CHECK(v == "v6.2.1811-3");
+}