welcome to the forum! hell I don't know... Let me see if I can figure out your terminology with ours.
1. not sure what a tang is, I'd think that was the end of something... No marking on the toggle?
2. Does it look scrubbed?
3. Barrel extension, is this the receiver and which side of it are you talking about? Eagle N (nitro proof) is a commerical proof so would be correct rather than the 3-4 marks on the right.
4. Was it buffed out?
5. it could be many dates...
6. does it look scrubbed?
Provide pictures and we can help, clear, light pictures
Ed