[600MRG] FT-37-WC toroid

[Paul N1BUG FN55mf]

Hey folks,

I am experimenting with MF and LF again.

I'm trying to source a few FT-37-WC toroids. They are .375 inch or
9.53mm OD, W material, epoxy coated. The only reference to such a part I
can find is Amidon. Of course FT-37-WC would not be what the
manufacturer calls these. Amidon prices and minimum order are currently
prohibitive. I would like to get the exact part if possible since I have
tested and know they work well in my application. Failing that I would
try a substitute, but I am unable to find permeability for "W" material.
Can anyone help unravel what these are, who makes them, possible
substitutes or sources in very small quantity?

73,
Paul N1BUG