One of the barely-surviving fast food outlets that has advertised their "foot long hot dogs" for something like 7 decades here now delivers a "foot long" that is a 10-1/2 inch long bun containing a weenie that is barely 9 inches long.
The bun possibly has not changed, but the weenie used to stick out both ends, which is what prompted me to check the measurement a while back.
I'm quite certain that the older wieners were a full foot long, since back in the time when you knew the workers at places of business that you patronized (late 40s?), a "famous jokester" of the generation before me liked to take a foundry "shrink ruler" in and make loud complaints about the weiner being too short - just as a tease of course.
At least a couple of the shops got in the habit of keeping a "legal ruler" at hand just for him. One shop nailed a ruler to the counter, with a sign that said "Check Us Out."