Hey-Hey!!!,
I have the listing for the 256. 20-20 Plus series. I can't find a listing for the 258 anywhere. I saw one go on eBay and have been trying to track it down since.I think it is a pair of 1250 CT windings, which can be paralleled, or series connection for 5k with what would now be 50% taps.
Until I find out what the 258 is, I will probably have to take down a 256 so I can wind up some custom OPT with taps where I want. 50% is not all that useful for what I hae in mind these days.
regards,
Douglas