I agree. It looks like a John Walch Navy Model 12 shot revolver (pg 374, "FLAYDERMAN'S GUIDE" 9th Ed).
This revolver used a cylinder which had 6 chambers.
Each chamber was loaded with two charges, one on top of the other.
The pistol had two hammers next to each other and two triggers, also with one next to the other.
The outer nipples were struck with the right hammer and fired the forward loads by pulling the right trigger.
Likewise the left hammer struck the inner nipples which fired the rear loads.
No mention is made by Flyderman about what would happen if the shooter fired the rear loads without first firing the front ones or what would happen if one of the front loads didn't fire and, in the heat of battle the shooter switched to the left hammer/trigger and proceeded to shoot all 6 shots. :hmm:
Oh, 5 years ago one of these Walch 12 shot revolvers in fine condition was worth $12,000.