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All RF transmitting devices sold in the US must be registered with the FCC. Somewhere on the transmitter will be an FCC ID number. You can take this number and go to the FCC Office of Engineering and Technology (OET) publicly accessible database and look up the "Grant of Authorization" for the device, which will document the frequency, power output, and type of modulation.
According to a Cochran manual I found on a German site:
Cochran uses 250 KHz
Oceanic uses 36 KHz
Uwatec uses 8 KHz
This probably explains why there is no FCC database entry for my Sol - 8KHz is actually an "audio" frequency so is probably exempt from Part 15 authorization requirements (I'm too tired to look it up now). There are entries in the FCC database for the Cochran units (250 KHz is a "radio" frequency).
Hope this helps.