Q: "I have two Chewing Tobacco cards with the first design. They are Flint, catcher, and Clarkson, pitcher, Chicago. They are both encased in plastic covers. Can you tell me the value of these or where I might find out this info?"
(Here's a example of a "first design" card from my site)
(This is one of the three possible backs from the set)
You can find some basic info about the set from my Vintage Baseball Cards website, but one thing you won't find there is a price. For that, here's a link to the set description from Old Cardboard, which says a common in VG condition can fetch about $145. That covers your Flint card, but the card you have of John Clarkson will be much more valuable since he is a Hall of Famer.
Buchner Gold Coin cards feature generic artwork rather than genuine photos, which makes them less sought-after than other sets. That said, there are enough collectors of 19th Century material that you'll likely get a decent amount if you are looking to sell them.
All of this info is assuming that "encased in plastic" means that they're either in the holder of a third-party grader (which will help you get a good price) or a screw-down holder.