Since the Kodak 2D was manufactured by the Folmer & Schwing Division of Eastman Kodak until 1926 when that division was spun off as the Folmer Graphic Corp and then, after the 1945 reorganization, by Graflex Inc, I believe the 2-D's serial number is a Graflex s/n. Certainly it works for the two I have. The older, marked as built by Folmer Graflex for EKC, is s/n 333745, the newer of the two is s/n 407056 with a built by Graflex Inc. for EKC. According to a list I have, 333745 would have been built by Folmer Graphic between 1941 and 1945; 407056 between 1946 - 1948.
The list of serial numbers I have is a xerox of page 14 from something by Richard Fowler but I don't remember what. The s/n are grouped in 2 to 5 year blocks from the start of production in 1887 until the end in 1973.
Over on the Graflex.org site they have a Q&A board where people help each other date their Graflex's. Someone with the screen name "Gandolf" apparently has the actual s/n list on a far more accurate basis than the gross one I have but he has not posted any responses for many months. Apparently blocks of numbers were assigned for the production of a given production run for a specific product.
bart