Advertised on Ebay for $20 shipped  as a "450MHz 100W amplifier running off 28V". The input / output splitters / combiners looked a bit lower in frequency than that, but at that price it was worth investigating.

The two feedthroughs at the RHS of the picture feed 28V to the source of the FETS which are PHI RF2212. The two feedthroughs at the LHS of the box are for a switched 28V supply for the bias network.

Sweeping the module showed a gain peak at 222MHz with a small signal gain of 17dB. At 450MHz it had a small signal gain of only 11 dB.

Driving it with a radio on these two frequencies, 2W on 222MHz gave 95W output, 3.5W input on 432MHz gave 45W output. The amplifier went into saturation very quickly above these values.  It did nothing on 144MHz.