Most of the H&R or Iver Johnson top break revolvers had an action that did not lock the cylinder in position UNTIL it was at the point of firing.
When the hammer is cocked, the cylinder SHOULD be locked in position. When hammer is down, free spinning.
These revolvers were made by the hundreds of thousands. If the caliber is marked ON THE BARREL, it should be OK with modern day ammo. If elsewhere, then it dates from the black powder era.
Yours appears to be in good finish. I would get a competent pistolsmith to look it over before shooting it. H&R and Iver Johnson made decent guns- they were not junk (and yeah, there were some junk guns back then) Prices were not high then- or now- unless you have one in like new condition.
What we have here is... failure- to communicate.