I'm soon going to have an opportunity to purchase 2 SP1 AR's that were (according to the seller) originally purchased by him sometime in the 60's. I'm a newbie when it comes to the vintage AR's, so I was wondering if anyone could point me in the direction of some info on serial number lookup for the older Colts. If not, does anyone at least know an approximate serial number that would indicate pre-1970 for an SP1? Thanks, in advance.