Expanding a little more on what 29-1 said, I measured (top of the stock through the escutcheon to the bottom edge) some target stocks of known age and here's what I came with:
plain, December 1952: 4 3/16 inches
plain, December 1956: 4 3/16 inches
checked, March 1955: 4 3/8 inches
checked, November 1955: 4 3/8 inches
checked (coke bottle type), February 1956: 4 3/16 inches
checked (coke bottle type), March 1956: 4 5/16 inches
checked (coke bottle type), May 1956: 4 5/16 inches
checked (coke bottle type), July 1956: 4 5/16 inches
checked (coke bottle type), December 1956: 4 5/16 inches
checked (coke bottle type), fitted to gun shipped in March 1958, but it is unknown if they are original to this gun or not: 4 3/16 inches
If you look at the revolver featured on the 1956 advertisement developed by S&W in December 1955 or January 1956 (see below), you will notice the stocks are most likely the same type I measured from February 1956. Why S&W increased the length of their checked stocks made for the new 44 Magnum by 2/16 inch is unknown, but it is these stocks most people know as coke bottle stocks (see additional photos below).
Bill
coke bottle stocks from July 1956 that measure 4 5/16 inches
coke bottle stocks on S147213, a very early 44 Magnum with stocks that measure 4 3/16 inches and appear to be very similar to the stocks shown on the revolver featured on the early 44 Magnum advertisement