This is a toroidal nanocrystalline (I believe finemet) core transformer with extremely wide bandwidth, depending of course on your driving source impedance. No faraday shield. Intended to serve as an input transformer, not output, so keep it close to the first stage grids.
2-wire input, balanced or unbalanced. 3-wire balanced output with center tap. No DC permitted.
Size about 2" square with 1.5" height with the hardware.
Asking $300 for the pair