Looking for help finding the origin of a 1937 U.S. postal desk

[littletaco]

I'm not sure if there is the place to ask but I thought I'd give it a try.

I inherited an old U.S. postal desk a few years ago. It's a nice piece of furniture but recently had to move some place smaller and it just doesn't fit. Looking to sale it but want to find all the info I can on it before I do. The family remember who gave it to me knows nothing about where it came from.

The only reason we know what it is, is because of two stamps on the its underside. One says "Property of U.S. Post Office. 123-Case. MFG-By John E. Sjostrom CO. 1937". The other is just "SDPO 1353". It also has a number scribbled on the underside of a drawer but I can't tell if it says 106, 901, or 701. I think it looks mostly like 106.

I looked around on the web and I think it might either be from either Warren PA or Idaho Falls ID but I'm really not sure. I couldn't find much information. I am pretty sure it was made by John E. Sjostrom Co. (since their name is stamped on it) which were based somewhere in Philadelphia ( I think).

I'm mostly interested in finding where it came from and what the numbers on the underside mean. But it would be great if I could also find what value it may have.

Thanks for reading.