I think it might even work - there are low-voltage tubes available: 12V for both heater and anode.
It is either anode or cathode follower topology, but it doesn't make it 'first in the world' and the signal quality might be questionable. There is no other specs except bandwidth - what about THD, frequency response, stability, EMI?
Great kit for DIY learning electronics (or is it accounting?). Cost of goods - $10 max (two tubes, wires, some aluminum pieces and connectors). The rest of the price - his 'genius' or assembly?
Yet another reason not to trust ebay - this guy has 100% positive feedback!
Vlad