And, oh, yeah...

A bit about the newly-introduced-to the story, Richard Luker. He was a Lt. in the USN in 1921, when his sub was sunk by a pilot boat named Philadelphia ( Evening Public Ledger of Feb 2, 1921) Thank you, Friend Safe.)  And, just coincidentally, he shows up again 39 years later in DARPA. (Once I would have quipped 'old dude' but I am chary of making such declarations now that they might well be applied to me.)

Is that almost 40 year span a normal USN career length or was part of his service, like Townsend's, spent in the Naval Reserve? And where did he report in the Naval Bureau Command structure that was in place at the time?