Re: colt single action army
Ist generation Colts (civilian models) offered many barrel lengths.
1st generation Colts (U.S. models) were produced with 7 1/2" barrels. There were several of these that later had the barrel shortened to 5 1/2", and are referred to as "altered models", or commonly called "artillery models". There were no nickel plated U.S. models. I have collected, bought and sold U.S. single action armies for the past 45 years.
The pawn shop most likely has a civilian model, and pictures and better description would help. Prior to purchasing, it would be very wise for you to have someone very well versed in 1st generations to check it out. I have seen too many pay way too much for what they were actually getting.