FWIW, I worked on a A&H made near the end of their existance, unfired, still in the foam box, but I don't recall seeing any documentation. Purchased from a broker, not A&H, as they had already ceased to operate. It was a percussion 54 cal Hawken-like rifle with a fast twist barrel, and a drum & nipple system.
Based on my experience, I'd urge you to carefully check out the piece prior to firing it. The new owner was cleaning the oil from the bore prior to firing it, and got the cleaning patch stuck in the breach and asked me to get the patch out.
The patch was stuck because the drum was about 0.20" too long and protruded into the bore. I started to remove the drum, and found it was only finger tight, the threads (metric of course) in both the barrel and the drum were badly stripped. I can only speculate if the drum would have been blown out or not, but the workmanship was somewhere between inept and outright dangerous. Maybe as A&H was ending their operations, they threw together whatever they had on hand to get stuff out the door.
I retapped the barrel to a larger US size, and made a new drum, fitted it tight. Owner has fired it and is pleased, but what a disaster it could have been.