He told me he got them off a antique store out there in Vegas they sold him a lot of different years this ones where extras of the same year.
You can't. The coin will grade AU at best. The grading fees will be almost as much as the value of the coin. From the images, I'm not 100% sure the coin is real. If it is real, you got a great deal at $7.50. That's about the price of just the silver.
because of the way certain letters are formed in Centennial, and more letters around the coin, I'm leaning towards counterfeit. The early counterfeits were easy to distinguish ... https://coinweek.com/counterfeits/counterfeit-detection-1937-texas-half-dollar-commemorative-coin/ The later counterfeits are much closer and correct the issues identified in that article. You can see the more current counterfeits on the various websites selling them. The counterfeits show many similarities to this coin, which still have certain issues on known non-fake coins. Truthfully, I was leaning towards "real" until you said you paid $15. Then I did more research in to fake identification, and checking out the current fakes, and comparing to real ones. I have some of these myself too so I'm familiar with them .. but them I'm no counterfeit expert anyways.
Well that's why I'm going to take them to get a professional opinion bc i did test that they are silver