Are we talking about an Ultrasonic Flow Meter? No, the Dynasonic is a unique guitar pickup from DeArmond (Rowe Industries).
They have been used on many guitar brands like Gretsch.
The Europeean guitar manufacturar Levin used the USA made Dynasonic on many off their models. There is no pickup which uses such large alnico bar magnets for each individual string. The adjustment mechanism is very sofisticated and durable (and expensive to make!).
Never put the magnets from the Dynasonic too close to the strings because the powerfull magnet can pull the string completly out of tune.
Rowe Industries stopped the production of the Dynasonic many years ago. Since about 10 years there are replica's on the market which all are as good as the old ones. I can't prove it but I think every replica (there are many brands who offer it) sold these days, comes from the same factory somewhere in...
The pictures show a Levin 320 from 1968