According to the book 'U.S. M1 Carbines Wartime Production, by Craig Riesch, there are three type of front sights for the M1 Carbine.
Type I: The Type I Front Sight was milled from a solid block of steel. There were minor differences in the machine cuts behind the sight blades but the sights were manufacturer-coded and are easy to identify.
Type II: The Type II Front Sight component parts were stamped from three pieces of sheet steel, formed and brazed or spot-welded together into a completed sight and adopted in May, 1943. They were manufacturer code marked.
Type III: The Type III Front Sight was a late, probably post World War II, cast sight, easily identified by the casting mark along the middle of the sight and used as a replacement only. The Type III sights marked "RIA" or "SA" were post-War Rock Island Arsenal or Springfield Armory replacements.
COMMENTS: All front sights were originally parkerized. Most front sights were manufacturer-coded except Winchester, Saginaw SG and some post -World War II cast front sights. the height of the sight blade may vary from carbine to carbine. Irwin-Pedersen and Saginaw Grand Rapids (IP or S'G') stamped a number between "2" and "7" on the left side to indicate blade height.
Based on the table in the book, a Winchester carbine of the 1 million serial number range would have been a Type I, which would have either been unmarked or marked with a 'L', which would be quite rare.
At any rate if you are planning on being a new carbine owner, this is a very worthwhile book to own.
