[723 regualtor as a swticher]
  I just checked what I have.  My 1977 Voltage Regulator
 Handbook doesn't list it at all.  My 1980 Linear Databook
 includes a couple of switchers among the typical applications.
 That would suggest such a data sheet would have to be
 around 1978 or 79. 
You want to go back much further than that. DEC were using the 723 in a
swithcing regulator circuit in 1972 (the date of my 11/45).
-tony