Stuff I kept the same, including but not limited to:
Coil construction; number of layers, order of layers, direction of wind....
Wire gage
lamination size and stack thickenss

Critical additions:
Additional taps for use in my E-Linear circuit. Different tap % provides differnet tube performance and different level of plate-to-grid NFB. Current build specification is 20, 30, and 40% which puts it at the convenient end of layer( there are ten for each half ofthe anode winding ). It also eliminates the original 50% tap. No sense having too many tap wires hanging out.

Made some modern substitutions for the old Kraft paper and polyester insulating material.

In two at a time construction two years or so ago, they were ~$100 each.

Price offered in the +10 quantity is $86 each. Line forms here if you want to get in on even a single. No requirement to buy a pair. These are quite versatile units. 10k a-a load, to 2, 4, 8 and 16R secondary. They are to be wound by Heyboer in Michigan and shipping will be in addition to the $86 each price.

The original Peerless 20-20 series S-265 was rated at 40 watts and nothing has been done to interfere or chage this rating on my modified copy. Can you say PP 845? I knew you could. It will work as well as a PP 1619 delivering a half-dozen watts in PP Class A operation. Look to the Merlin schematic in the projects folder for a proven schematic for this OPTx.
cheers,
Douglas