[GreenKeys] Hi speed reader foto...

[Jim Haynes]

You're probably thinking of DX, the high speed reader, worked up to 2400 
wpm.  DRPE is the punch that was supposed to take the place of the BRPE
and work at 2400 wpm.  BRPE was limited to 1050 wpm.

The 750 wpm you are thinking of was probably Dataspeed Type 5, which used
the CX reader and the DRPE punch at that speed.  But most of the stations
were send-only, with reception right into a computer rather than punching
tape.