Pre 64 Model 70's are considered to be the holy grail of rifles by some people. I really like them, but I like all model 70's no matter when they were made.
I think the serial is how you tell the date, someone who knows more than I will chime in I'm sure.
I've seen some pre 64's go for $2,500 But the cheapest I've seen one is $1,200. I'm sure there could be even more variation than that.
Give us some pics, we love our gun porn.