[GreenKeys] McElroy keyer - Wheatstone tape?

[Nick England]

Thanks to Tom Tillson's manual, I got my newly-acquired ex-USN
Wheatstone perf making all the right holes in paper tape (after
building it a 110vdc supply).

So I hauled the McElroy XTR keyer (10wpm to 200 wpm ) off the shelf
and started cleaning it up.
http://www.navy-radio.com/xmtrs/control/keyer-mcelroy-91.jpg
http://www.navy-radio.com/xmtrs/control/mc-67.JPG

Looks like it works OK, but not the way I expected:
I figured there would be some mechanical latch mechanism for the
hole-reading contacts that would close to form each dit and dah.
But no, it appears this device has separate start and stop contacts,
and depends on some external device to actually turn those signals
into each dot and dash to key the transmitter.
i.e. for a dit, the start contact closes briefly , then a little later
the stop contact closes briefly
- for a dah, there is a longer pause between the start and stop closures.

So, does anyone have any clues as to what the required external
"flip-flop relay" would look like?
I mean, I can certainly build something using IC's or tubes, but what
was really used to run at 200wpm back in the day  (1941 according to
the date on this keyer).
cheers,
Nick K4NYW
www.navy-radio.com