[Arran]

It's probably 1930-31, or possibly as late as 1932, since it's an obscure off brand, the #24s and #45s debut in 1929 but were pretty well standard by 1930-31. The reason I say that is it appears to have the power switch mounted on the volume control since I can't see any wires directed to a bat switch on the side of the cabinet. If you look at most other makes in 1929-30 the power switch was independent of the other controls, either as an extra switch or knob on the front panel or a switch on the side. I wonder if the power supply box has electrolytics or large non polarized paper caps and chokes inside?
It's an interesting cabinet design, it has sort of a Eastlake look to it, Eastlake was a simplified style of late Victorian furniture. I have a few antique chairs that are what one would call Eastlake style, it was very popular, even up until WW1, and is therefore quite common to find even now. In any event it was a nice find, regional makes always interest me in that they would do unique things that one of the big national makes would not do. Brenda Ann was right about the stylized "S", I didn't see the little bumps around the edge of the circular opening, perhaps Sterling had ambitions of becoming the next G.E?
Regards
Arran