I was back in the local candy store owner's office today (he works for me in his other life), and noticed an H&R receiver on his desk. When I picked it up to see if it was a SB1 or SB2 I discovered it was a Topper 158.
Now, it has the typical old H&R finish (gunky brown!), and some dings around the receiver pins. I figured some back-alley gunsmith tried to do a trigger job, and this was confirmed when I found the hammer wouldn't stay cocked and the trigger won't return forward.
He said the gun came to him with no stock and that he had a barrel for it somewhere (did I mention I have to supervise him closely?). No idea of caliber/gauge.
So, if anyone is interested PM me and I will give you the details.
Les