My dad has the chance to buy an old coach double barrel shotgun. It has a shield in the stock marked Wells Fargo. It was made by Springfield Armory. Anybody have an idea about value?

Make sure you find someone who can verify it's authenticity. W.F. & Co. marked guns have been faked many times. You might try someone like Ron Peterson at Ron Peterson's Guns in Alburqueraque NM. He is very honest and very, very knowledgeble about these type of things.
Just be careful and don't get taken.

I know someone who was having Wells Fargo brass plates made and then putting them on old double barrels. He sold a lot of fakes that way.

that's an unusual way to get yourself killed...

Rich