FWIW Burroughs also used drives/platters like this
with their small systems
 (B80 - B1800); ISTR that they were ~ 5MB but 32 SPT instead of  12 or 16;
 unfortunately I dumped all of mine long ago. 
I can remember when the Inmac catalogue (that dates me...) told you
to count the number of notches in the hub, subtract 1 (for the index
notch) and order the appropriate pack. I can't remember which ones
were listed.
Didn't the DEC RK01 use 8 sector packs? Something certainly did.
-tony