Used to run into these on a fairly regular basis. There's also the same thing but built on the 150 pistol frame... yes, a 50 cal. model 150! As far as I am aware of, there are no regulations in the US for procession of this type of gun.

For some time, at least initially, these were built by Crosman Assoc. which was PY Hahn's personal little factory out back. There are no records on what was made there. What's happening today, I have no idea but they're still using Crosman airguns as the foundation for their products.. the last I looked.

One interesting thing about the chap chur rifles is that over the years they seem to have made a whole bunch of variations. If anything, I can't recall ever seeing two that were exactly the same.