If they are from the reserve, I think you have to open the rolls. The rolls with the P's have "N.F. String and Sons - Harrisburg PA" on the rolls. I doubt the coins from Denver are shipped to Harrisburg PA for rolling - but who knows. From the mint - they are marked D and P on the wrapper.
If the mint uses a single source vendor (which would make sense) then yes they may use the same wrapper at different or the same facility regardless of mint location? In that case you may have to open the roll to find out
Well, I just answered my own question. I just received two rolls from a forumite in Minnesota that I sent two rolls of P mint's to. They were exactly the same rolls, N.F. String & sons. I just opened one, and they are D mint's.
By opening the roll, and looking at the coins inside. BTW N.F. String & Sons is a company headquartered in Harrisburg, PA, which manufactures both wrapping machines and the paper rolls they use. It sells empty rolls to banks, armored car companies, the Mint's contractors, and others; but doesn't wrap coins itself.
