What's inside this mysterious safe dropped in a farmer's field?

This rusty safe turned up on the edge of farmer Kirk Mathes's field in Barre, New York. Apparently a note pasted to the safe said the contents belong to whoever can crack it. While Mathes was traveling, words of the safe spread and a crowd attempted to pry it open to no avail. Apparently police intervened and, upon his return, Mathes had the 500-600 pound safe moved into his barn. Mathes claims he has no intention of opening the safe but would prefer it to go to a history museum that the town is planning. From 13WHAM:

"If you open it, the show is over. In these times, with the virus and the politics, it might get people a chance to set their problems or troubles aside and have a lot of fun talking about it," Mathes said[…]

"I don't know where we're going to hide it – but as soon as you leave, we're gonna," Mathes told 13WHAM's Tanner Jubenville.

My guess is that it holds Al Capone's secret treasure or, perhaps, a piece of dank carpet.