DAM16SXS,
Research made by C. Price and S. Fjestad, on actual Parker guns, published in "Parker Gun Identification & Serialization" (p. 45), shows the following distance between strikers: Frame 000 (13/16"); Frame 00 (15/16"); Frame 0 (1"); Frame 1/2 (1 1/16"); Frame 1 (1 1/16"); Frame 1 1/2 (1 1/8"); Frame 2 (1 1/8"); Frame 3 (1 3/16"); Frame 4 (1 1/4"); Frame 5 (1 5/16"); Frame 6 (1 3/8") and Frame 7 (1 7/16").
According to this research frames 1/2 and 1, and frames 1 1/2 and 2 share the same distance between strikers. This tells something about the (later) origin of frames 1/2 and 1 1/2. All the other frame sizes have incremental distances (1/16") between strikers right as you mention, but one: Frame 000 that goes down 2/16".
Regards.
