I believe there are four distinct Model 52 pistols.
1) original no-dash 52's, made from 1961-1963. Supposedly 3,500 made. These have the old style extractor and this extractor is a scarce part if you have a problem. These guns are actually DA/SA, but the DA can be locked out so that the pistol operates strictly in SA mode. All of these have a 5-digit serial number that begins with a 5.
2) 52-1, made from 1963 to 1970ish, these guns have no DA ability and it is often said that the sweetest 52 triggers ever are the 52-1 pistols. These also have the old-style long extractor that can be difficult to fix if you experience a failure.
3) the A-prefix 52-2 pistols, these have the newer and more modern coil-spring loaded shorter extractor and are perhaps the most "popular" to own and shoot, these ran from 1970-ish to around 1984, these are the most popular mix of everything including modern extractor, deep blue finish, "old school" and collectible & shootable.
4) the three-alpha prefix 52-2's that ran from 1984 until production ended in 1993. These often aren't as bright, deep blue and the wood stocks are often of a lighter and plainer grain, these were the last of the 52's and may generally be regarded as perhaps a bit less sought after than the A-prefix 52-2 pistols.
Which is the one you want? Probably #3, followed by #4 and then #2 and #1. I have a pair of #3's and a #4 and the #4 is what I love to shoot... I would love to have a #2 next.