Finding the age of my 700 just by the serial number has been kind of a challenge since the barrel letter code was machined off to make it into a lighter #1 taper. You are correct with the 700 sn's starting with the four digit sn back in '62, but I know that I read something about the changes to the 700's starting in 1968 and probably with that 6200000 sn 11/68. That puts my 7mm RM 62485xx into mid '69.
Back in 2013 Campfire member butchlambert1 wrote: "700 receivers with ser# 1000-387347 started in 1962 until 11-68. 6200000-6899999 started in 11-68 until Aug of 1975. A6200000-A6899999 started Aug 1975 until about Jan 1980. B numbers were from 1-1980 to 11-87. C numbers started from 11-1987. This is as far as my John Lacy book covers."
Those early sn 700's shared a lot of the same features as the 721's it replaced with some cost saving modifications though I'm not sure how they differed from the later 700's.
