Just wondering about coins that are on the map - If a player puts a scout there, do they "harvest" a coin like they would Iron or Silk? Thus getting a coin and adding it to their total? Or do they just count that coin while they have a scout on the square, and when they move off they reduce the number of coins accordingly?

You do not harvest coins from squares like resources.

The coin is added to the player's total (and subtracted from an opponents if it is a blockade) while the scout is there. As soon as it leaves, the coin is lost.

While the scout is there, the coin is theirs. When the scout leaves, the coin goes away. So...the second thing you said.

Ah, but Bismark does have a coin on his map. If the coin is in the Outskirt, then it will keep that 1 coin at all times.

Thanks for the information, I thought it was a gathered resource, but even tech cards have a "max" limit for coins.

It should be noted that a scout delivers a coin from a tile at the Start of Turn rather than immediately (even though it looses it immediately if the scout moves/is lost).