Definitely late 20's-early 30's-I've seen pictures of later A-B sets but every one I've seen in person was around this age. The design around the dial is unique. I checked the books I have but none pictured this one but I did a little googling and came up with model 48 (looks there were a lot of variations). Here is one to check out:
https://www.radiomuseum.org/r/americanbo_48.html