.
Boy! 'Mountain Crest Estate' is a tough nut to crack!
...I just finished an hour or two of searching.
Let's review:
We're talking about an early subdivision, right? And
, per the 'firebreak' sign
, the location (560 acres)
has to be somewhere between Topanga Canyon and Laurel Canyon.
My guess is. . the 729 Central Building is in downtown Los Angeles.
(or perhaps Santa Monica?) 
Although I didn't find any information on 'Mountain Crest Estate' I found a half dozen or so rabbit holes that I plan to revisit.
Fun times!