Near the end of this level there is like a compass on the wall with three gold pieces missing from it. I know where to are one is in the professor's bedroom and the other is up the stairs. Does any one know where the last one is and how to get it?

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All Achievements Retail: 9 Arcade: 3

I think the last piece is behind some doors, but I don't know how to open them.

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All Achievements Retail: 9 Arcade: 3

Never mind, i got it.

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All Achievements Retail: 9 Arcade: 3