I'm looking to perfect the entire game and would to know if there is a way to tell how many gold pieces you've grabbed on a retro level. The game only marks the level with a star after you beat it, but doesn't actually show you a ratio of gold pieces you've grabbed in the level.
Here's an answer with screen shot: "Is there some reason to get all the gold in the retro levels?"
tl;dr: the only place retro-gold seems to count is on the main map, in the lower-left "Totalés Grandé". No way to distinguish which level the gold is from, but the retro levels do contribute towards the total.