In the few months Lionel was making trainsets in 1945 and early 1946, numerous changes were made in the flying shoe coupler. The best resource on the variations in the flying shoe coupler is Greenberg’s Guide to Lionel Trains, 1945 to 1969, Volume II, Behind the Scenes, second edition.
Flying shoe couplers were used mostly in certain sets. The tinplate Pullman series in 1946 all used them. (blue 2430-2431 series, green 2440-2441 series, brown 2442-2443 series) Sets 2101 and 2103 used them (Same or similar items to those in the 463W with the 3559 dump car thrown in.) and in the early O-27 sets, specifically sets 1405 & 1411. Flying shoe couplers were also dabbled into sets 1409 as usually a car or two have flying shoe couplers. Someone else can determine what a representative number would be.
As to electrically operating flying shoe couplers, I recommend against it. The very tiny spring is 70 years old, maybe rusty, and the only way to repair it is to pry off the head, replace the spring if you can find one, (like from a different broken flying shoe coupler) and gluing it back together. It is easier to just replacing the entire coupler. Repairing later slide shoe couplers is a walk in the park
As to the universal frame for the tank cars, I believe it was stamped 2955-17. (I’m on a trip and don’t have my train shelves handy) And though the part number remained the same, the frame was strengthened by filling the open sections on the ends starting with 1946 production on the cars numbered 2555. I defer to Pete for decals and placards for 2555 and later production, but add there were two variation of 2755 decals on the 2755 tank car and two variations on the Sunoco decal as well in 1945 production.
Dan.
