About 15 years ago a friend sent me his reel tape collection of interviews he had made while doing a religious news show on the BBC. He asked only that I might convert one or two tapes to cassettes for him. Upon playing the tapeS! I found they were, in fact, recorded at about 5 ips!
I did the best I could at the time by increasing the size of the capstan until it came close to c. 5 ips.
Evidently some recorders (for radio use???) recorded at 5 ips, or nearly so. Else, why were there several such tapes?
P.S. The man was Rev. Eric Robinson, and his show was "Man with a Mike". He interviewed numerous famous clerics and theologians just after WW II.