Fire control system calibration. There's a lot to balancing a gun in a combination mount. If you stabilize a gun sometimes you have to off set balances and tolerances that were unforeseen in the design that only come up by putting the eye to the sight and squeezing the trigger.

Even a modern mount like in an M60 series tank has spots for weights to offset imbalance. Ever see a tank that no matter how you bore sighted it it couldn't hit a target because the gun and sights weren't calibrated properly? Ever calibrate the FCS in a tank?

That stuff. So sticking a pipe on the bottom of the gun to correct imbalance can actually work just the same as a couple of fishing weights on the back of a 105mm.

And is a 10 degree angle is discernible from a front 3/4 view? Or under a pile of baggage? The angle is only on the center of the rear over the exhaust. On a Lee and Grant the rear to the sponson was the same on all variants. So you can't tell from any other angle than directly to the rear or precisely from the side without any hull rear storage. The South African Grant OP tanks were photographed from those angles so you can see they're Grant II with Grant turrets and diesel engines, anything else? Guess your best. With 300 tanks shipped they must have shown up some place as replacement tanks. And there is one clear photo of one in North Africa in combat.

And why am I replying to this? Use your imagination and stop being so pedantic. I have stuff to go off and create rather than debate angels on the heads of pins.

T24053 and T24061 were apparently radial diesel Grants - and one might assume also the numbers between 53 and 61

Some might enjoy this timely walk around of the subject tank.

https://www.youtube.com/watch?v=_p7eJr0grTc

BTW, where do you guys get your information on vehicle serial numbers - such as the T numbers allocated to Grant Diesels in a reply above? In other posts here and elsewhere I've seen people identify trucks and other vehicles just from their serial number.