915 identification and value

[joe18d]

I have a 915 transmission that I picked up a few months ago. The number on the bottom rail is scratched / worn and unreadable. Would sanding it possibly help expose the stamping? The date code on the side cover is 20/76 and the Porsche part # is
915-301-102-1R. Are there any other numbers that may be helpful in identifying it? The seller did not know much about it and got with a purchase of a a parts collection. Any help is appreciated.

Thanks, Joe in NH