When did production of the #13 cab begin?

[David_Hayward (RIP)]

My notes, just found, suggest that the # 13 Cab dates as follows:

The No.13 cab introduced a large number of improvements and modifications, which were agreed upon tentatively at a meeting at 7 Corps HQ on 22nd December 1940, of the Standing Committee at which Brigadier N.O. Carr, D.M.G.O., N.D.H.Q. [Deputy Master-General of the Ordnance], produced photographs of a new type of cab which would provide greater crew comfort and better engine access. He also mentioend that the engines in these trucks should run between 5,000 and 10,00 miles without attention other than provision of oil ans water.

This was taken from Dr Gregg who must have read the relevant file at the Archives in Ottawa though I have not had that pleasure yet.

Brigadier, formerly Colonel, Noel O. 'No Car' Carr was the DND's 'father' of the CMP. I often wondered if he retired as a Major-General.