National Application Notes AN1(1967), AN8(1968) and
AN2(1969) show the LM100
 regulator IC in switching configs. 
Interesting. It looks like the rumour I heard about the 723 is false, in
that it was known it could be used as a swticher from the start.
  The LM100 looks like the predecessor to the 723, a
reference and error amp in
 one package. It disappears from later databooks, presumably obsoleted by the 723. 
I think that's right. I cam across an LM100 in something recently,
probably something old and HP. Maybe a 6940 multiprogrammer???
-tony