What does @version return for all clients. Here is an up to date list including the latest versions of LotusNotes.

114 Notes 3.x
136 Notes 4.0, 4.0x
138 Notes 4.1, 4.1x
145 Notes 4.5, 4.5x
147 Notes 4.6
166 Notes 5.0, 5.0x
190 Notes 6.0, 6.0.1
191 Notes 6.0.2
194 Notes 6.0.3, 6.5

198 Notes 6.5.5
256 Notes 7.0

261 Notes 7.0.1
262 Notes 7.0.2

266 Notes 7.0.3

301 Notes 8.0

307 Notes 8.0  Basic Release 8.0 Revision 20070803.1143

If I'm missing one let me know.

You can also do lotusscript notessession.NotesBuildVersion to get these values.

You can also do notessession.notesversion.

This returns a text message eg: "Notes Release 4.1"