Found this picture reference 'Library' quite by chance as am gently looking for a BSA underlever of the earlier type, so doing quite a lot of research.

Treat yourself and have a browse. Picture examples (with serial numbers) submitted by owners covering Lincoln, Standard, Model D (and B), Ladies, Junior...
...rare Military Pattern....
....and best of all: with details on variations, accessories, etc

Just fabulous stuff!

http://www.network54.com/Forum/670443/

and....
....if you only have time to look at just ONE...
....then may i suggest the following as the ultimate customisation...
http://www.network54.com/Forum/67044...SA+Light+Model