There are a lot of idiosyncrasies between Crabs as evidenced in photos. Take this pic I posted above, which according to the Imperial War Museum is one taken prior to Operation Goodwood July 1944. The vehicle shows, what seems to be, the storage box attached to the side of the vehicle but has the mounts at the turret rear. The tank has T49 track links and where the station keeping equipment usually is, this vehicle has the fire extinguisher - plus no mounts for any of the marker boxes or pole device on the hull rear sides:
And a still from the Tank chat video showing another tank with the box on the side:
Some video that may be of interest about 1 minute in for each
