Daryl and NitroX have it - the firing pin is recessed

Controlled feed - yours is as my Field's Patent (posted here)where the spring loaded firing pin is flush with the block - note the slot underneath to allow the hammer to fall far enough

Also, for your interst, note there is what appears to be a 'dig' in the top of the breechblock of the A-H. This is actually a machined semi-circle
This ties in with the lip on the bottom of the hammer

I only recently found out its purpose
If you lower the hammer to rest on the sidewall when the breech is open, insert a cartridge and close the breech sharply, without this notch and lip the hammer could flip down and hit the firing pin with enough force to fire it!

When the lip engages the notch it will prevent the breechblock rising

Alexander Henry was a very clever guy!

TH44