IIRC, the first units I used were 200 bpi!
The vacuum "columns" were instead "rows". They extended about a foot
to
either side of the heads.
Gil
Also, it was only the NEWEST drive that had 6250 bpi.
Mostly
we dealt with 800 and 1600 tapes, and with drives that had
switchable 7/9 track heads. I wouldn't call vacuum column
drives an icon of EARLY computers...