S: located after finish by the disconnector on top of the frame indicates field service. Located on top of frame by disconnector indicates gun inspected by Ordinance Inspector. Bullet feed ramps where blued in receivers to serial number 710,000, then at SN 710,001 they where machined after the receiver was blued or parkerized, leaving this area of the gun in the white and unfinished.G: Located on top of frame by disconnector indicates gun was made to fill a Government contract. This area should show machine marks and not be polished. You'll likely find the year and 'IMBEL ITAJUBA' or 'FI BRAZIL' stamped under where a grip goes or on the bottom of the dust cover.
Only by studying lots of pistols will one know what he is looking at, and that is getting to be more and more difficult. Also remember that when metal is stamped it is pushed a side and will create a ridge.In 1999 Colt released the XSE Series Model O Pistols.Features of these guns included front slide serrations, adjustable Mc Cormick trigger, three dot dove tail rear sights, ambidextrous safety, enhanced tolerances, aluminum frame and stainless steel slide.From 1970 to 1976 the serial numbers had a prefix of "70G", from 1976 to 1980 they had a suffix of "G70" which changed to a prefix of "70B" from 1980 until 1983 when production ceased.In 1983 the Series 80 Models were introduced with an additional passive firing pin safety lock and the half-cock notch was also redesigned.