IIRC SEPTA had picked the Ascoms because their hardwired scanners made them less expensive, and at the time of purchase the Treasury hadn't done a major bill redesign since the days of Bulldog Drummond
and Paul Whiteman. In any case by the time the new 20s were released most outlying machines were already gone, at least on paper due to those reasons of maintenance and vandalism.
A number of BOBs lingered at Center City stations, presumably because they weren't as difficult to care for. Problem was, they could only be upgraded by physically replacing the scanners - not exactly cheap versus e.g. a software flash. Instead SEPTA went through a couple of [email protected]
$$ed "solutions": First, they just put up signs telling people to only use old bills. After the old bills disappeared, they installed change machines next to the boxes. Passengers weren't exactly happy with getting a pile of quarters and dollars that then had to be fed into a BOB, and it wasn't much longer before all of them were gone.
FWIW I attended a hearing shortly after the new-bill problems surfaced. I'd come prepared with a buffalo nickel and Indian head penny, and asked the SEPTA suits if they were the next step in fare payment. They were distinctly unthrilled.
Requiem for it's/its, your/you're, than/then, less/fewer. They were once such nice words with such different meanings...