Have a look at the meter (carrier level indicator) on this photo of an
excellent condition pre-WW2 RME 69.
Calibration is 0-72 db in six db steps, with a lower scale clearly in
S units, going 1-9 every six dbs.
The photo is good enough that you can read the "RADIO MFG ENGINEERS"
and the PEORIA, ILLINOIS, U.S.A. in the meter face fine print.
I think the RME 69 is mid thirties. This is back when you had to read
the manual to see what the knobs did. Notice the complete lack of
stamped lettering around the knobs.
So the IDEA of an S unit being 6 db is quite a bit older than some
have put forward. Whether this one is any better than modern receivers
at displaying real signal levels is anyone's guess.
I'm intrigued as to what process was used to create the dial
calibration for the main tuning. Photo offset of a hand-drawn master?
This is part of an EBay auction at
I watch the ads for the occasional excellent photos of these old
pieces of equipment.