Lucas,
The post you reference from the LC-USA forum is mine. The measurements were taken from original '60s Giuliari literature I have. The TV/2 and early TV/3 seat (possibly other models, depending on market and dealers) is often referred to as a 'Coke bottle' (US) or a 'wide-end' (UK and RLC). These seats differ from Giuliari model 1425 (as fitted to the Special, and possibly others) and Giuliari model 1876. From the pictures you posted above, your seat is a 'Coke bottle'/'wide-end' seat. The central flat bar across the middle of the seat, the flared shape, the 2 central springs, and the screw in rubber buffer are all unique to this Giuliari. RLC are selling covers for these seats, which I believe, are made for Casa by Dante.
If you want to donate that old cover to me, I have a German mailing address I can share