well, making props for movies in the industry vs making REPLICA props in a hobby for profit are 2 very different things. Like most watches in movies when not shot close up are usually fake or empty cases that are used in Salesmen sample trays. You really don't think "James Bond" is running around with a real $5,000+ Omega watch on his wrist the whole time...
MIT could have either donated a ring or gave permission to make a 1 off copy, that wouldn't be mass produced and sold to non alumni. Or bought it in a pawnshop, who knows.
Replica props are a touchy subject, but when you're dealing with replica name brand watches and jewelry it gets even touchier! They're much more hardcore than the studios. Hell, designer David Yurman actually sued and WON against several other jewelers he said were copying his designs, when he takes some of his designs straight from Celtic/Norse art. Some how he was able to copyright an ancient form of art!
I'm not saying you can't do it, I'm just suggesting you think twice about it. I'm in the jewelry industry and also in the prop hobby, so I kinda know that it might lead to a bad situation.
- Jeff