Is there any trick to knowing if an item is r99? I'm going for the Valuable Pawn achievement, but short of hovering over each item to see its rarity, I can't find a way to find r99 items in the Pawn Shop.

Maybe there's a userscript that highlights r99 items (not just in the Pawn Shop but all over the site)??

It's highly unlikely that you will find a r99 item in the Pawn Shop because so few people use it, and if they did they wouldn't pawn a r99 item because it isn't worth the sP. The best way to get the achievement is do it yourself. Find a cheap r99 item (Twilight Serpenth Trading Card is one), pawn it, then buy it back :)

Great idea, thanks!!