That's an inauguration medal for Thomas Jefferson, not a Corps of Discovery medal. The reverse does display the design of the medal that was given to chief members of native American tribes by the Corp of discovery, but it is not a Corp of discovery medal.
Didn't know they made these in pewter. I've got the silver version still available at the US Mint....
The company that made this is still in business in Bristol, TN. They have a very nice web site, apparently will make you custom items.
This is a copy of the Indian Peace medals that Lewis and Clark took with them on their exposition. They were shell medals (hollow inside because the first mint could not strike solid medals of that size.). Lewis and Clark gave them to significant Indian leaders. The U.S. Mint made copies of these pieces for many years. I don’t know the origins of this one. Five dollars is a fair price for an educational piece like this.