The information I've able to find on the Mk4 shows the loaders hatch was eliminated and the TC got a new hot tub sized hatch. My question is why does Mengs Mk4 have a loaders hatch?Are these turrets rebuilds, or did they decide to put the loaders hatch back on? I'm sure the loaders feel better about it.

Early production vehicles did not have a loader's hatch and are usually seen without the .50 cal on the mantlet.

Later production vehicles had a loader's hatch and were equiped with a .50 cal.

Sometime along the earlier variants got retrofitted with the loader's hatch.

Initially, the Mk.4 was designed without loader's hatch to maximize armor integrity, however later studies proved that the advantage of the stronger armor was largely offset by the reduced chance of the loader to escape the vehicle. Some of these early variants were later retro-fitted with loader's hatch.
Generally, the omission of the 0.50 cal on the early variants was due to the fact that it's (mainly) operated by the loader; it was introduced later as part of the LIC upgrade package, however, there were (are?) early variants also without loader's hatch but with 0.50 cal mounted above the gun.

Nikos, Thank you so much for the information. I know the Sherman originally came without a loaders hatch, but that was changed in relatively short order. It's like The Chieftain says in his video on the Sherman: Ya gotta give the crew a chance.

Especially when you think that the crew is more important than the tank.

Very good and accurate answer dear Nikos,

When the Mk. 4 was designed, the tank was produced without a loaders hatch. However, Maj. General Israel Tal decided that all turrets will be machined for a loader's opening, will be covered with a special dummy hatch, and will be covered with the roof armor module, so if IDF will regret, and change their mind, an easy retrofit will be implemented.
And it happened exactly as forecasted.
Now days, all serial Mk. 4M with "Trophy" active defense system have the loader's hatch + a redisigned roof armor module.
All Mk. 4 are in final stages of retrofiting the tanks with a loader's hatch and replacement of the armor module.

Michael Mass