Does this AZO "squares in corners" in the "place stamp here" box mean the card was created post-1920 with no exceptions?

Here is the site I use as a guide - it says 1926-1940s for that one:
http://www.playle.com/realphoto/

My Trade/Sale Page

jeff,
you should get david rudd's book. it's excellent. pm me if you need any info, i have the book at home.
best,
andy

Thanks! I'll check out his book. Does the book say anything about possbile exceptions to the 4 squares dates or is it impossible that this card can be pre-1926?

It's pretty certainly from the dates Playles have on their site. What's on the front?

No exceptions -- that paper (it's photographic paper with the postcard-ness printed on the back) wasn't manufactured until 1924. (Playle's date, but AZO dates are pretty well established, they're the most common of rppc papers.)
David