Zenith Super 7

[H. W. Petersen]

I'm in the process of fixing up a 1924 Zenith Super 7.

After taking the radio out of the cabinet I found the following inside
the cabinet on the bottom where the radio concealed them:
1. An embossed paper label stating "Stout Smith Trust, manufacturers of
high grade cabinets, Salem Indiana, and containing a small logo with the
letters STS.
2. Three characters, 3/8" high, stamped into the wood in this order -
capital S, a delta (or equilateral triangle), and another capital S.

The two letters may refer to Stout Smith but the delta doesn't seem to
fit in. (Delta has several meanings in mathematics and physics notation
but they don't apply here.) Can anyone tell me the meaning of these three
characters?

Thanks,

Pete Petersen