Yes - on worth and junk.
Looks like a basic L-pad device with some switches - like a Carl's or Bugera PS-1.
I wouldn't run a vintage 100w through it, but it still may be useful.
Downside risk = $40, or maybe just offer $20.
I say pass. I just found this picture on the internet and it's slightly bigger than a pedal so probably can't handle a larger amp. Attenuators that can handle larger amps are heavy. My Alex 100W attenuator is almost the size of a shoebox and weighs close to 8 pounds.
Good attenuators cost good money. And weight and size matters.
EDIT: found this thread, it seems to be some kind of resistive load. Still not worth it.