[Lynn Eades]

Nigels book refers to 2000 Universal, Mk1 Carriers being allocated to Australia.
The numbers allocated were T75594 to T77593. This was contract no. A1071.
I doubt that orders always equalled deliveries, and maybe the balance of Australia's order was filled from a later contract. The fact that your carrier is badged as a universal, and it's T number is allocated to a Mortar carrier, is probably indicative of many such anomilies.
As it happens, there is very little difference between a Universal and a 3" Mortar. It's common to find carriers with holes for fittings from other models of carriers, which have been blanked by rivets. It would be easy to convert a Universal to a Mortar on the production line.
Back to your question,in short, I can't answer your question.
How about some photos of your carrier?