How To Learn About Long-Standing CO?

[segaloco]

So I hadn't noticed before today that all the dial cards I currently have are 206 734.  I wasn't surprised by the area code, as I live in western Washington, but the central office code being the same, coupled with the fact those are all local purchases, had me wondering if 734 was the building I know downtown to be an old PNW Bell CO (today still telecom, CenturyLink/Lumen.)

After a bit of searching around I realized hey, I don't really know how to go about figuring that sort of thing out.  Is there any sort of BSP, Bell System documentation, or something else that would give hints as to which CO I might be looking at, if I can trace these phones to their mothership?

On the subject of this building, I've also been trying to find pictures from before divestiture to get an idea of the signage, but have thus far been unsuccessful.  I've got a few local avenues I'm following to see if I can find some historic photos, but I was wondering if there might be similarly some Bell-adjacent registry or something that would've had photos or suggestions of building plans with layout of signage and such.  I find myself walking by it sometimes (as it is on my daily walk) thinking...Where was your bell?  Where was it?  A silly piece of trivia sure, but a piece of local history at a crossroads with my interests that hopefully I'll dig up some more info on.

[SUnset2]

According to:
https://www.npanxxsource.com

360-734 is Bellingham REgent
1201 N Forest St., Bellingham, WA 98225

Google maps:
https://www.google.com/maps/@48.746668,-122.477516,3a,75y,348.74h,96.9t/data=!3m6!1e1!3m4!1snW6J-Sp4XYjz35ODA4v-8A!2e0!7i16384!8i8192?entry=ttu

[segaloco]

Hah, it is exactly the building I thought.  Well based on the information over in my 500C/D thread, they might have some WECo 5ESS stuff up in there...maybe.  You learn a little more every day.  Now I've got one more fun little piece of local history trivia, now if only I can find those darn historical photos I'm searching for.