Are you sure that's the serial and not the assembly number? The serial is on the butt. I ask because according to this other thread I'm reading, I cant find your serial. I know this other thread is a good starting point, but also that it is incomplete because I can't find my own serial on it either.
So... According to this, all I can figure is that the model was introduced in 1977, and that's the best I can do.