I have an old shotgun that had a bad barrel. I'm stubbing it for a muzzle loader barrel. It dates around 1902 and is marked Harrison andd Richardson. ...Yeah that's the correct spelling. Anyway, it looks a lot like an H&R.
Today at a gunshow, I picked up an old Columbia shotgun and it is the same gun, just a different name. I did a little research on Columbia and it seems most of the world manufactured them at one time or another.
Harrington and Richardson did make them for a while. It looks like the steel spacer will fit a modern handi and I think some of the other parts like the hammer and trigger will work also.
I'm going to try the spacer tomorrow and maybe modify the forend as well.
Could be a good source for steel spacers.