I had a couple of 16rpm (actually 16 2/3) records; as mentioned above, usually 7" like a 45 or EP & only for speech - typically giveaways at conferences & fairs on really cheap plastic, not even vinyl. Possibly some plays were recorded on full size (12") @ 16-2/3, which would give 45 minutes or so per side, but I never saw any.

Being an old fogey, oops, I mean folky, I even had a wind-up totally mechanical phonograph (78 rpm natch). I can remember when 45's were the latest thing, and then 45 EP's tried to compete with 33-1/3 LP's, unsuccessfully. If I remember rightly, one of the big record companies came out with the 33 LP and another very quickly brought out the 45 as competition offering higher quality (in theory) because of the speed; rather like the VHS/Beta competition.

How on earth did they come up with those speeds anyhow?? I mean, 78 rpm? Why not 80, or 90? And then 33-1/3 ??? Was there a studio standard of 100 rpm that somebody divided by 3?
TP