The different 'overprints' from different cities seem alike because the USPS in Washington supplied the precancel devices to the various post offices. They were manufactured by a government contractor and the styles had consistency, although they varied some from year to year. So, 'making' the vinyl devices was a standardized process in most cases.
The inking and printing on the stamps also might seem alike - but with a little practice, anybody should be able to make nice clear impressions. The seller of these particular
ebay items is probably the 'maker'. He has been to many small towns in recent years. He is well known in the precancel community. However, up to about five years ago when the USPS seriously cut back on precancelling, many collectors scoured the USA to get current stamps precancelled - so the precancelled transportation coils come from many 'creators'.
I include them in the precancel states I collect: AL, DE, MT, VT, WA.