It looks like a suet block to me or maybe just a seed block the same size as a suet block. Suet block feeders are often small green cages.
That's what I told my wife, suet feeder. I have never used one here. I have been told the heat would break them down fairly quick. The seed block may work if I trim it to fit in the feeder. it is maybe 2" radius so not very big. A little bigger than a "Pringles" can.