Marksman model 70

Ok guys first post. I have a marksman model 70, that I think was made by Weihrauch. I'm in need of a rear sight. On the barrel there is what looks like a base with a pin in the front. What do I need to order to put it back in operation. One more question if I go the other direction , and install a peep . Is the scope rail 11mm like I see on the peeps advertised. Any help would be appreciated. 
 
i'm waiting on a .22 barrel for ny marksan 70 .... i think the rear sights are supposed to be different (could be the safety) - something on this gun is supposed to be made by bsf , and i think they preceded weirauch ...

MODEL 70 

- .177, .20, or .22 cal., BBC, SP, 19.75 in. barrel, blue finish, 925/760 FPS, 8 lbs.

Manufactured for Marksman by Weihrauch, using B.S.F. tooling.

..... bluebook data... in any event , check back with me after the holidays , and by then i'll know if i'm gonna keep the snubby .22 or leave the long .177 barrel...either way - i dont use open sights (cant see poop)... here's a link to mine (i wrote about it) : https://www.airgunnation.com/topic/marksman-model-70/