Neil, I am still here
I am glad Colin was able to help.
Indeed, some Cab12's were fitted with square roof hatches from the factory; I have seen at least C15A's and C8's fitted with hatches in factory pictures.
I hadn't noticed before, but at least two different C15A Cab12's with Wireless house type bodies were in the Utrecht parade in June 1945.
source:
https://hetutrechtsarchief.nl/beeldm...ows=1&page=134
https://hetutrechtsarchief.nl/beeldm...ows=1&page=138
https://hetutrechtsarchief.nl/beeldm...rows=1&page=94
