[Collins] wtd : info on a strange PTO ?

[Wn4i]

Back from the Orlando ( FL )  Hamfest  I came back with  a strange  PTO
very close the same as a 51J3-J4 PTO .
I didn't find  it on my list of Collins PTO's .......?
The name plate is as follow :
DUBROW Electronics ind. Burlington NJ
Type 689-BM128 ....ser. 1864
V801 5749/ 6BA6W
V802 5749/ 6BA6W

With a 7 pin mini plug and only one Coaxial out .....the only real
difference is that is surounded with a heating coil and a triangular
termostat on the back .
As usual it is a  10 turns ( actually a 11 turns )
Any idea of the frequency coverage ?  and the radios it is coming from ?
Any infos welcome
73
Yves Wn4i
Yves Pautard
5833 Dryden rd.
West Palm Beach
Florida 33415.....561-689-8819