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Allo R,
I'm afraid I don't have access to them or pictures for a while. I will try and get some towards the end of next week.
However, I did just find an old post of mine on one of the other forums ... I think this should give Bud a decent idea of what I had.

The device is basically a vertically sectioned bobbin.
The bobbin is a solid nylon cylinder, outer diameter 70mm, length 78mm.
Into the cylinder were turned 17 grooves. Each 3mm wide, with separation 1.5mm between them.
Can't remember how deep they were, but  I seem to remember 5 or 6mm.

Into each groove was wound a winding section. There were 9 primary sections, 8 secondary.
My winder managed to get 220 turns in each primary section. Afraid I can't remember the wire gauge used. Total of 1980 primary turns.
Secondary was something like 3 (!) turns per section, 24 turns total,  for a ratio of about 82:1

The windings were arranged P-S-P-S....-P

results:
182mH for the primary

Driving from a claimed 600 ohm sig gen output, I got a bandwidth (-3db) of about 650Hz to 48kHz.
This, btw, is at a ratio of 82:1 into a 0.5ohm load...

Hope this is of use.... you know, you could probably get a *magnificent* OPT along these lines for the upper S2 as well...
Following your theme above, I'd be inclined to omit the bobbin and have the coils naked...or maybe dipped in hot wax to provide just a little support....

cheers
cv

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