The piece was given to me by the staff at the Monteclair Library when I did a month long exhibit back in November 2001. (URL) the part comes from the L.O.M sets. Their included in the sets that contain the minifig explorers and that base. (sorry I (...) (23 years ago, 31-Jan-02, to lugnet.build.mecha)
I'm also fairly certain that 2 x 2 round tile comes in the T-3 Trike set. I have one of those, but not one of the shuttle sets, so I'm certain that's where I got it from. -Dave (23 years ago, 1-Feb-02, to lugnet.build.mecha)