QUICK START: Ideally enter 3 or more of the letters you can see on the Postal Cancel and then determine if you believe the letters are at the Start, Middle or End. Then click the appropriate button under "Search Type". Click Unsure if you are unable to determine.
The towns that appear will narrow down the possibilities of the actual Town cancel. Then using the PMC or PMI you should be able to determine the town the postal cancel is attributed.