Several names have been stamped on these but are known as model B-3. I used to sell these years ago.Cleaned up and smoothed out they will print dime sized patterns at 25 yards all day long. 850 fps and a rifled barrel.
I have one in .22 that has a scope mount that is pinned on one end while the other clips loosely on the back of the "reciever" also has iron sights. Also have one in .177 that has grooves on the barrel for mounting scope rings. What scope mount is on that one of yours?
I mounted a Lyman peepsight on it, drilled and tapped.
Mines a .177, well the one I kept is. used to go through 500 rounds a week. Every week, living in the county near a cattle yard drilling sparrows. Was not uncommon to drop them at 100 yards. Ever had yours apart? Not that hard to do.