Is This A Congressional Gold Medal?

Yes, Dr. Thomas A. Dooley III was awarded, posthumously, a gold medal by the US Congress. Bronze duplicates of the 3-inch medal were sold by the Mint for years. I'm not aware of silver versions being sold.

The overall design on your piece seems very close to the US Mint piece, but not exactly the same. For one thing, it appears to be in lower relief. For another, the figures on the reverse do appear to be an exact match of those on the Mint medal. Without having them side-by-side, it is difficult for me to say whether the differences are an artifact of your images or are truly present on the medals. Also, the Mint pieces with which I am familiar do not have a rim.

What size is the piece?

Standard sizes for modern US Mint medals include 1-5/16" and 1-9/16" which equate to 33.3 mm and 39.7 mm, respectively.

So, the size of your piece, along with the design differences mentioned previously, make me think your medal might have been struck privately (i.e., outside of the Mint) even though it clearly mimics the official US Mint piece. I'll continue to check my references and will post anything else I uncover.

Although I do not know if they were issued for the Dr. Thomas Dooley medal, there are on occasions silver examples made of congressional gold medals, especially if examples of the medal are awarded to a group of people. Although not done often today, there are also Congressional Silver Medals which can be awarded to individuals separately from the Congressional Gold Medal.