even more I think this explains the "T14" comes from

see this drawings, so first is listed as MT-Tug , normal vehicle
https://www.team-bhp.com/forum/iipcache/144559.jpg

and the prototype with gun on it is called "T14" but it's not actual vehicle designation just some trial prototype
https://www.team-bhp.com/forum/iipcache/144561.jpg


https://www.team-bhp.com/forum/4x4-vehicles/116115-willys-super-jeep-6x6.html