At some point in 1944-45 the pattern for stowage on Cromwell tanks was changed. Initially the turret was bare of stowage boxes: But there was a stowage change which added bins on each side of the turret - you can at least see the right side of the turret here: Does anyone know why this was changed? Also when exactly?
Looked this up in both the Osprey book on the Cromwell by David Fletcher and the HMSO book on the Cromwell tank. The Cromwell has a series of hull and turret types throughout its service life. The turret storage came about with Hull Type F (Cromwell VI and IV). This hull was the first to include a driver's side escape hatch. The installation of this hatch meant deletion of some of the side storage bins. If you look at the photos you've posted you can see the top picture has side storage bins flush to the front where the driver is peering out. On the bottom picture you can just make out the escape door on the left side and the shorter storage bins, no longer flush with the front of the tank. This was mirrored on the driver's side. The turret bins were to replace this lost hull storage space.
A type hull, both driver and gunner doors opened upward, there were 4 external boxes on each of the wings. B-E type hull, drivers door opened upward (was either 2 piece or 1 piece) and gunners door swung outward (one box was lost on gunners side), drivers side still had two. F type hull, both driver and gunners doors swung outward, only 2 external stowage boxes on the wings (so needed external stowage boxes on the turret). Issue with top opening hatches is depending on where the turret was rotated, they would not open, and the crew member could be trapped. A type Hull B-E type Hull F type Hull