I recently bought two #2 rolling blocks and I'm in love. Everything about them is perfect for me. My question is that one is in 38/40 #28638 and the other is #42664 in 32/20. I then got another in 32/20 as a parts gun #42694 [made within a week of the other?] but the breechblock on the 38 is different. It extends above the rear of the receiver and has a notch cut into it which I can only assume is to serve as a rudimentary rear sight. I imagine that this is a pistol breechblock that somehow found it's way onto a rifle but I don't know. It looks original but who knows?  Any thoughts?

It sounds like the breech block with the "V" cut in the top is from a Rolling Block pistol.