I took a chance and bought a T generator at a local car show. It works and just needed a new bearing - I replaced both.
But the brush design isn't like other T generators I have seen. The third brush has a clamping bolt which will slide in a slot when loosened, but the slot is much larger, and so is the bolt. The bolt is also the mounting for the brush spring, and it has a nut with a 1/2"AF hexagon. See red arrows on photos
Also the dust cover is a fully formed cap which is retained by a single screw, rather than the usual clamp type. See photo.
Has anyone seen this type before? If not, could it be a UK 'improvement'?
Early FA Liberty generator used for short time on Model T Fords in 1918/1919 T. Has unique brush plate, third brush, brush spring and brush cap cover.
Would you believe they also had their own special Z-wrench? I have one of them.
A lot of the first electrical stuff was weird compared to later stuff. The earliest ammeter did NOT have the Ford script on it and was a very elegant design mechanically with some nickle plating on the internal parts. The ignition switch was nickle plated casting on the paddle portion of the light switch. The ring gear on the flywheel for the first starter cars was aligned to the flywheel with dowels around the perimeter. The cutouts were all sorts of shapes and sizes before being mounted on the generator. Some were square some oblong and some had extra terminals not used at all. One of the round can cutouts used a cover made from copper. Fun stuff.
Well, I've learned something. I'm indebted to you all. Thank you.
And I've got a good spare generator at a good price.