I was at the gunsmith's shop today, picking up the last of my guns he has refurbished after The Incident and subsequent house fire.
He showed me a couple of old topbreaks in for "restoration." One had been prettied up with bumper chrome and looked like a chrome plastic cap gun, the other pretty ragged in peeling original nickel plating.
Neither functioned and the replacement parts said to be suitable did not fit.
As I said before, do not give a gunsmith a blank check.
I am not qualified on your registration requirements, but will say:
Bottom - Iver Johnson serial #C12448
Almost surely "modern" the type was made up until WWII.
Top Left - Harrington & Richardson serial #401 165, says "32 S&W CTGE" on barrel
A "smokeless" model made after 1905. "Modern."
Top right- Harrington & Richardson serial #12336 on handle, # is G12336 under cylinder
This one is the tough one. With no caliber marking, it is a "black powder" model. but all that means is that it was made before 1905. I don't have anything to say whether it was made in 1896 or 1904.
Ammunition: We make distinctions of "black powder guns" vs "smokeless guns" based on what was in use when they were made or how proof tested.
However, .32 and .38 S&W are not loaded any hotter than they ever were and are no different in external dimensions. It is not like they were .32 rimfire, which is almost unavailable, you can buy a box of fresh smokeless ammo and cut loose with them. They might not last as long, if you credit discussions of pressure curves and such, but they will shoot and probably won't blow up.
If I were a bureaucrat, I would say that ammunition is "readily available."