Stock date of 2455 means the 245th day of 1955-roughly sometime in the month of August 1955.
IHC rifles are hard to date precisely by either barrel date or stock date as both stocks and barrels were made and dated by other contractors who supplied them to IHC. These dates are the date of manufacture, not the date of assembly to an IHC receiver. Stocks were made by Overton, and some will show the initials "OR" in addition to the 4 digit date. IHC used barrels made by Line Material Company, marked LMR in connection with the drawing number on the side of the barrel. LMR barrels have an excellent reputation for accuracy and many were used to build up match rifles. I have found them to be great shooters.
The latest dated LMR barrels that I have seen on the IHC rifles produced in late 1955/early 1956 are dated 3-55 or 5-55, well before these rifles were assembled. IHC rifles which were built on IHC made receivers in the first 9 months or so of 1955 will show LMR barrels dated from late 1953 to mid 1954.
There is a book pending on IHC rifles from a well known collector which should better illuminate the story of the IHC Garands. I have had some exchanges with him on both IHC Garands and the M1C sniper rifles, and I consider him to be a real expert on the topic. One thing for sure, IHC produced the fewest Garands among the 4 US makers and they are a very desirable collectors piece.