Tank Census Number

[sri130]

I was searching some classifieds and came across a '41 WM20 with a census number starting with 'CA'. With some searching I'm falling short of understanding what the second letter actually means. I thought genuine census numbers were just C followed by numbers. Other than some Canadian CC numbers.

I'm still a novice in my understanding, but hoping you can help.

[Dean Southall]

Perhaps a 4 was mistaken as an A.
Anyway, you find an answer here: http://www.wdbsa.nl/index.htm