Unfortunately this isn't quite correct.
Originally Posted by Kawaiithulhu
Graflex Inc. and predecessors assigned serial numbers sequentially in blocks (smallest block size, 1) from the beginning until the introduction of Pacemaker Graphics in 1947. So for cameras made before 1947, s/n carries no information about which model has it.
In 1947, Graflex Inc. changed its procedure and assigned large blocks of serial numbers to Pacemaker Graphics by type (Speed, Crown) and size (2x3, 3x4, 4x5). In 1949 another block of serial numbers was set aside for the Century Graphic. So Century Graphic and early Pacemaker Graphics serial numbers identify the cameras by type and size.
And then later in 1949 they merged the Pacemaker Graphic s/n blocks by type and started assigning serial numbers by size within merged block. From then on, serial number can't be used to tell a Speed Graphic from a Crown Graphic.
I haven't checked, so could be mistaken, but I believe that Graflex started putting a metal s/n plate on the inside of the outer bed (= front door) with Pacemaker Graphics. Before then the s/n was stamped somewhere on the inside of the box.