Will other barrel such as Topper work on this?
Just sportster rimfire barrels such as 17m2, 17 hmr and 22 wmr.
Receiver has a rectangular firing pin that is built off center to impact the rim.
I don't know what it's worth in today's market but $200 for sure a few years back. You can probably make more by parting it out and get $200 for the barrel, $60 for the receiver and $60 for the stock set.