It should be stamped into the metal itself. Underneath the emissions sticker (if you still have that),just to the right of the hood latch on the core support. If you have the sticker but don't want to remove it you can feel the underside to see if you can make out what the code is.
Hard to see in my photo, but it's there. "831". I'm only able to make out the 3 and the 1 from the bottom side of mine.
For anyone looking, Zcar Depot sells oem rear control arm rubber bushings for the 510 now. Just ordered a set through their EBay store, $85 bucks or so shipped. Sure glad I didn't settle on poly back when I first started looking.
Goof off works well too. I just let it saturate a rear door weather strip, came back as hour later and the seal came out all in one piece and left almost no adhesive behind.