US machines have always been interesting to me.

Some US domestic games, stamped US, left the USA. I've unloaded them from containers from Europe, marked US, and it's been clear it was a US game. Some from Brazil as well.

Some machines are sold on the black market. There were issues with Sterns being purchased in the US, loaded on containers, and shipped to Europe, being sold cheaper than folks could buy games in Europe. Yes, Stern's distributors had a fit. The solution? Modern Stern games won't work without a CPU board swap, because the transformer has a different hz rate in Europe than the US IIRC.

Most of these things can be worked around. It's like when WMS put security chips in games, to stop bootlegging of games outside of territories. A basic circuit would turn the DMD off until the game had booted, therefore making it impossible to get the serial # off the PIC chip (shows when the game boots, normally)

The most important factor, IMO, is to make sure the game is in nice condition. A lot of Americans don't like games that left the US and came back, and try to value them lower than a game that never left the country. Condition is king. I used to help a friend unload containers so I could get the pick of the litter. I've bought some operators out who had poorly maintained games that made even the poorest condition container games look 'minty'.

WMS games had country codes, but I've never found a way to completely decode them. I've studied it quite a bit. Wish I knew exactly how they did that.