SAE 77 is the year in which it was granted acceptance by the Society of Automotive Engineers. Although acceptance is sometimes granted in the first year of production, it often took one or two years to gain the acceptance seal. A better indicator of exactly when a warning device was made would be stampings or tags bearing a date inside the bar or on the motors. That is a nice looking SVP bar, kind of a rare find. I don't that particular bar enjoyed much popularity, I think I've seen only one or two in service.
Oddly enough, the SAE date on turn signal, marker light, and tail light lenses was an excellent method of determining the model year of American made cars and trucks. In this case, if the SAE dates didn't match it was a sure sign that the lens had been replaced for some reason.
