You're on the right path, Alton. Notice that the 1947 to 53 Lectrolite, the 1953-62 SK-Lectrolite, and the Dresser Era SK Tools 1968-85 are all the identical wrench. This is why I say that the 1947 Lectrolite is the SK RP wrench. Other than details like finishing and markings, these RP remained essentially unchanged until the closing of the Defiance OH plant in 2010 at the Ideal takeover. The older SK combination wrenches have a great reputation for quality, which gives you some idea how good the Lectrolite products were, even though they're like Rodney Dangerfield in that they usually don't get any respect. Even the budget Tru-Fits are really good wrenches, the main difference being the reduced cost from using far less metal in the recessed panel and lower quality finishing.
You'll also notice in the photo the difference in the lettering font where the earlier ones have generally thicker and wider characters with an 'open' C and the 1s having a serif 'foot' while the later have an almost closed C with no foot on the 1. This change occurred sometime during the Wayne era.
From a tool history perspective, it's interesting to note that SK made essentially the same wrench design from 1947 to at least though to Facom, and the RHFT ratchet first introduced in the 1930s is still being made today. How many tool companies can claim that many years for a single unchanged distinct tool design, let alone two?
SK is VERY cool!
