I would search Longmont CO. The town was started in 1871. https://en.wikipedia.org/wiki/Longmont,_Colorado It's a medal. You might find some edge lettering.
This type of medal is an OFFICIAL. If it had a stated face value it would be a token. If it then listed the name of a merchant it would be a STORE CARD. They are issued looking like coins. Embedding it in clear plastic or acrylic is an after market modification that most generally lowers the value. Earlier issues of this type are frequently called SO-CALLED DOLLARS. Modern ones like this are not. These things rarely bring a premium price because most people who want them already have them. Occasionally two homesick locals will get in a bidding war and surprise you. I agree with the statement of Longmont being in Colorado but I'll check my place name sources and add to my comments if others exist.
Looks like a token. Search for the name on it. As for being old, well that's relative. It's dated 1971 and that's 49 years ago. To some that's old but to others it's not.
Medal, a token has some kind of an exchange value, it can be exchanged for some specified thing or set amount of money in trade.
This dealer owns a coin business near there. He might know something about it as he's also member of the local chamber of commerce http://wwwchamberlaincoins.com
Just tell him you have a 1871-1971 Longmont Centennial celebration medal. And you were wondering if it had any value. Most of these are valued by there metal content. So knowing if it is silver or a white metal is a plus.
