I have a M77 in 284 made in 1987. From what I've read this was a very small production run, does anyone have any idea how many were made during this run? How does the value compare to one of the older ones made in the early 1970s? Also, the serial number on the bolt is about 175 numbers off from the receiver serial number and ends in "SP" - (special production ??). The gun doesn't look to have been messed with in any way and is in like new condition. Was it common for the bolt serial number to not match the receiver?