Wanted: bridge plate

[Keith Orpin]

Maurice,
Could you let me know what the correct diameter and thickness of an original bridging plate would be ?
I've also just noticed another interesting twist on bridging numbers. I've always believed that my C30 LAAT should have 6/10 shown on the bridging plate, however, it you look at the original factory pitures of a C30 LAAT, it's shown as 9 on the plate. Now, would it be that the British showed both the vehicle weight with and without the gun being towed (ie 6/10), and the Canadians gave a rough combined weight (ie 9)
I await your learned replies,
Regards
Keith