@sabi First one I actually remember was definitely 56.6K, though of course it only ever connected at 48.8 (or 33.6 on a bad day) because phone lines are a thing. I think I may have used worse on my grandmother's or father's systems when very very young, but not sure.
I will never, so long as I shall live, ever forget what the dialing/connection tones sounded like, lol.
@nazokiyoubinbou you never forget modem connection sounds. You could turn off the speaker but I’ve never known anyone that did!