A timely question for me. I'm writing a piece on variations in the early PW era 1944-49 for a presentation at the TCA convention at Warwick and that icludes cataloging locomotive variations for those years. Here's what I have on the turbines.
1946 - Smoke lamp, E-unit controiled by plug in cab - no boiler slot, nickel rims on all drivers, 671W tender, marked only on box.
1947 - Heater type smoke unit, E-unit slot in boiler, nickel driver rims, 671W tender, marked on tender.
1948 - Blackened rims on first and fourth drivers, 2671W tender.
1949 - No rims on drivers, new type of brush plate without tubular brush holders. 2671W tender.
The above information from Doyle'sStandard Catalog of Lionel Trains 1945-1969.