RAY-5 Receiver, type PR7NA

 I bought this WW2 receiver made in 1944 on impulse. It looked interesting and came from the Welsh town with the very long name.

My guess is that someone bought it many years ago as government surplus and (a) had trouble finding anything technical about it and (b) discovered nothing much could be done with it to get it working as anything useful. It's a crystal controlled receiver with an RF input around 25Mc/s... but what was it designed to be used for exactly? The meter suggests perhaps a homing signal, and the output being a coax socket perhaps fed something complicated rather than mere headphones. I suspect the name Doolittle provides a clue which is "do little", however it was designed for the Aeronautics bit of the US Navy so maybe it was a sonobuoy receiver, akin to the ARR3?
 The thing has its own HT power supply fed from a dynamotor. Lots of valves but two are missing. The list is as follows:- V101 6AB7, V102 12A8GT, V103 12SJ7, V104 6AB7, V105 6AB7, V106 12AC6, V107 12H6, V111 12SN7GT, V110 12SN7GT, V109 12SJ7GT, V108 12SR7 plus a crystal on an International Octal base. This is marked Bliley Elec Co. M54A 6766.67Kc/s. As the crystal is adjacent to the 12A8GT I guess it mixes with the incoming RF to produce an IF. T104 perhaps is an IF transformer with the 12SJ7 the 1st IF amplifier?
 Under the chassis a typical US designed layout and US components from WW2. the 28 volt power input is fed from one (or both) of the two identical connectors at the left.

You can see the pristine internal condition in this view. Not bad for over 70 years. 

 Here's the opposite side, just as clean.

 And the end view.
 The various labels on the set. Right, this is on the outer case, below the front panel, and bottom right the label on the dynamotor. No shortage of information.  

Below a description of an earlier model circa 1939 using a standard range of valves and a different power supply.

 Now, what do I do with it?

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