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.
Around that time there was a portable tape recorder that used a spring motor capstan drive with a large external flywheel. It used the motor for a 78 rpm turntable which was set to run the tape at 7-1/2 in./sec. however it is likely that the governor could be adjusted for a slower speed and a clever technician might have made this adjustment to allow longer recording time, since for broadcast the tapes would only have to be played back on the same machine and transferred in the studio.
The same tampering might be applicable to other portables that used DC governed motors and 5 in./sec. might be about the limit of the usable range of such adjustment.