Salvage Square D "Watt Transducer"

I have salvaged out an old control panel NEMA enclosure to build my much delayed staged RPC control panel. It had some really cool bits including some nice heavy copper blade switches (8), terminal strips, fuse blocks, and a "Watt Transducer". What is this thing and is it any use to me? Seems like some of these things are used as voltage transformers and such in control systems.

It is a Square D "Watt Transducer".

Class 8410
Cat. No. CLE-204002
2 Elem, 3 Phase 3W
IN: 120V 5A 60Hz
Out 1mADC Into 0-10kOhm at 1000 Watts.

Useful? Sell? I did some google research and couldn't find anything that really made much sense. My friend gave me this box and contents to help me on this project. If I can make use of this, then I will. But it appears (from the search) that it's worth a few bucks. So if I can't use it, I'm going to return it to him so he can make the profit. Wouldn't be right for me to profit (other than from the gift as intended) and he does ebay stuff all the time...

It's a very useful device, is what it is, providing an output proportional to wattage (real power), as you no doubt have gathered. But only useful if you need a reading of real power.......

They are indeed expensive, varying in the several hundred buck range new.

They do differ in scaling, and some are probably more useful than others, depending on what you are doing.