Australian Car Number

[Mark McKibbin]

I have just picked up my chummy (1500 Km away) it is late 1927 by the chassis number 51146 it is probably a Holden bodied car, no external door handles, steel body with swage line it's been fitted with a later coil engine sometime in it's life but otherwise it's a runner that needs some love.

There is a car number mounted on the NS door pillar as per the photo, I'm a bit suspicious as the numbers are engraved, shouldn't they be stamped? Does the CH mean it left the factory as a chassis or am I reading too much into this?