Manual tape splicing made that cash register loop.

Yes. Roger Waters recorded a bunch of cash register sounds (the ding, the drawer, coins hitting metal, even a paper being torn), then physically cut and spliced the tape into a looping 7/4 rhythm using a razor blade.

This was the late ’60s / early ’70s. No samplers, no digital editing. If you wanted a repeating sound, you literally glued bits of magnetic tape together into a loop that ran through the machine. The “Money” loop was constructed that way — different segments of sound cut to length and taped into a continuous circle. Then they recorded that loop onto the multitrack and played it during the song.

The weirdness of the 7/4 time signature came from how the tape pieces were cut. They didn’t plan it mathematically. Waters just kept splicing until it sounded good.