Hello, I bought an old building kit off of eBay, and it has some white-ish powdery residue on it. It seems thicker than dust, but may just be that. Has anyone seen this before or know what it might be?
Since it's plastic, you should be able to solve the problem by just washing it with soap and water without hurting it.
Is it a brick building? Maybe an attempt at putting mortar in between the bricks for a realistic look?
If no signs that it was ever damp, whatever it is should be harmless. Could it be from some sort of release material from the original molding machinery? I would carefully wash the plastic parts in barely warm water with a very little added dish soap. Rinse thoroughly.