Here's a suggestion for sellers
In the subject of the thread put your location in between brackets, like:
[AU], [UK], [US-WI], [US-NY]
So an example title would be
FS: 19" arcade monitor [UK]
WTB: Empty jamma cabinet [US-FL]
Also in the title might want to put willing to ship overseas or local/pickup only.
At least put the country in the title, state/province is nice for local/pickup only.
This will make it easier for buyers and traders to locate threads they are interested in and in their own country.