I actually spent a fair amount of time trying to research this issue a few years ago, but was not able to come to any firm conclusions. The US DOT did not come into existence until 1967, and based on my analysis of the Code of Federal Regulations, it does not look like there were any federal regs applicable to the number or location of truck clearance lights until about 1970. So the only clearance light regs were by the states and provinces, which differed quite a bit. Some only required the two on the corners, some the three in the center, and some the five we have today. Many states exempted farm vehicles from having any clearance lights. A friend here in Md has a 7E28 that was originally owned by the FAA, and it only has the single center light bar with the three lights so we know that in 1962, the Feds were not requiring five lights. Federal agencies always equip all their vehicles in accordance with then-current federal regs.
I have never found any clearance lights with Stude part numbers on the box, though I know that Stude did list them as a factory/dealer accessory. I dont know who supplied those that Stude sold. The Feds did have some regs regarding lighting even before the DOT was established for example, sealed beam headlights were required in 1940, and tail lamp lenses have had to meet visibility standards (and thus have been dated) for many years. (Police used to use the date on the tail lamp lens to determine the year of a car, which made sense back when the design changed every year. That doesnt work any more, as the same lenses are now used for many years.) Some time around 1968, clearance lights that met DOT regs started carrying letters on the lens, like DOT 70 indicating that the lamp met the standards in place at that time. So any clearance lamp with DOT lettering on it is too new to be correct for Stude trucks.
Ive been combing Carlisle and other flea markets for years, and can tell you that all of the clearance lights Ive found that are old enough to have no DOT lettering are chrome teardrops with glass lenses. There may have been some made with plastic lenses, but Ive never found one. I do know that the round red and yellow reflectors you used to see on old trucks were made in both glass (and plastic after WWII) inside a steel or aluminum body, so its possible that plastic was used in the old days.
I have some NOS clearance lights made by Yankee that are dated 1960, but without the DOT lettering, so I know that some manufacturers dated their light designs even before the DOT was established. My 4E40 was a farm truck in Sask, and came with no clearance lights. I havent decided how many to add on. Most of the trucks pictured in the ATHS show magazines have the full set of 5, but I think that many of them were added later during restoration. The big truck culture demands a lot of lights, and authenticity is not highly regarded.
Posted on Aug 7, 2012, 9:09 AM from IP address 22.214.171.124