If you’re in London, this weekend is your last chance to see Neil Armstrongs Underwear. The Wellcome Trust History of Medicine exhibit is closing down on Monday, and one of it’s best kept secrets is going with it.

I was lucky enough to have been on the last ever tour of this Gallery, where I got to talk to one of the curators. I was told that this “Urine Collection” bag was taken on Apollo 11, and that the astronauts who used these tended to write their initials on them to make sure that they didn’t get mixed up.

The initials on this pair are “NA”.

The Medical History Exhibition will be back in 2017, but this historical artifact may not be on display. It’s actually on loan from the Smithsonian, so they might take it back. It’s one of the Science Museum’s best kept secrets. It’ll be gone by Monday, so see it while you still have the chance.