1946 series Hxxxxx Ixxxxx Jxxxxx A0xxxx (small type face) Bxxxxx
Cxxxxx (low number)
Cxxxxx is probably a cusp number between 46 and 47. More on the 47 side.
1947 series Cxxxxx/Dxxxxx
1948 series Dxxxxx ect...
Identifying features:
Skinny drop outs (1946)
Razor edge fenders
Shortie rear fender(early 1946 rare)
light cover has deep rear screw hole
Raised or de bossed style AS clamp(rare)
Non scripted light lens
Tapered pencil kick stand
Canti frames have more of a hump to the top tube. (Early)
Straight bars ie "fat bars" have same dia bottom tubing. (This feature also was found on later years and is not solely indicative of a 1946)
Rack clamp is a one piece flat band aid shaped plate.
Rear top stay fender bracket is sometimes tubular on early frames. (I've only seen this on dx models). My 46 rear fender stay mount is taller and more boxy then late 40s 50s style.
Early 46 tanks have been seen with tapped brackets ie left over snap style prewar tanks.
Big outtie delta horn button and tank hole (prewar size).
Chain guard front frame mount tab is thinner with bigger hole.
Grips will be oval with one tail coming off N without double back crossover(late prewar style)
Rear chevron will be shorter on 46.
Drop center rims or sometimes Lobdell flat profile rims.
1946 bikes have been found with 1941 stamped dogleg cranks
skinny truss rods.
Springer pivot bolt rumored to be chrome on early 46?
Pivot clip was prewar style half clip.(early)
Springer fenders sported diamond and tombstone reinforcement tabs
Granted stuff got replaced or got carried over ie pencil stand.
Note; (A) serial started again in 51 but in regular larger print.
What I have gathered doing research and asking experts is that the I J and K serials would have been left over prewar BB shells and or frames that had already been stamped prior. A being the first true postwar serial.