If you are indeed considering purchasing an M1A, pay attention here!
From the July 03, 2007 draft of the Third Edition of M14 Rifle History and Development:
Bolt - Springfield Armory, Inc. M1A bolts are manufactured in the United States of America. The M1A bolts are typically marked 7790186-SA on the first line and A00030, B00048 or F00059 or similar number on the second line. They may have markings such as D and M3 on the rear end and A9 or B1 on the bottom surface. The letter A prefix for the number under 7790186-SA means the bolt was cast then finish machined. The letter B prefix for the number under 7790186-SA means the bolt was machined from bar stock. The letter F prefix for the number under 7790186-SA means the bolt is forged. Springfield Armory, Inc. began installing F prefix M1A bolts by no later than 2000.
See 1987 Springfield Armory, Inc. Recall Notice for additional M1A bolt markings. No M1A parts, including bolts, are made by metal injection molding. Around receiver serial number 165###, Springfield Armory, Inc. commercial manufacture factory installed bolts have letters and numerals with a taller and thinner font than the style found on USGI M14 bolts. A Springfield Armory, Inc. M1A bolt not subject to recall was tested for surface hardness. The result was 52 HRC, the same as a USGI HRT marked M14 bolt.
When I look at buying an M1A, I make damn sure it either has an F code bolt or a real GI one, beware of the A code bolt!!!
On that note my best M14 rifle is now a custom USGI build on a forged Polytech receiver and it came in at $200 less than a M1A standard costs.
Many M1A parts are made outside the USA and their quality has suffered over the last several years. If you can find an older one with GI parts that's fine but the newer ones are not worth it anymore.
I have owned and shot M1A's for many years, but they're not what they used to be.