It looks like an unremarkable medal, possibly silver, look for .999 or .925 or Sterling on it, including edge. It's a great story but the value is probably best keeping it in the family, as you probably don't have his signature or any documentation of this. So it's worth $5 or $35 depending on metal content.
My Grandfather was stationed in Mexico City as an Attache for the United States Government. After the Apollo 11 astronauts completed their mission to the moon they visited Mexico City. My grandfather was tasked with showing the astronauts around while my grandmother hosted the wives. During their visit, Buzz Aldrin gifted my grandmother this silver medallion as a thank you. This medallion was presented in its current state, as a necklace, by the team.
I would love any information y



