The subject of the factory/supplier applying a identification paint mark was posted over in the 68 section. Didn't want to post the ones below and take the discussion off the focus
https://www.concoursmustang.com/forum/index.php?topic=30833.msg185987#msg185987Looking through my paint mark collection of pictures I found the following.
Didn't get or save the one on the lefts source but the example on the right is from a 69 San Jose (9R02R131xxx) 4 speed Mach 1. Believe this is from one of my ex cars so it was Power Disc Brakes

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