Here is a picture of my M4A3E2 "Jumbo" you can get a good idea of the glacis thickness by looking at the keyhole cut for the bow gun, as well as how much thicker it is than a non-jumbo differential which is installed in this case so we could throw tracks on it and have it sit for static display until we get around to it's restoration...it is #73 of 254 built, one of only 6 or seven left in the world, and I am sure the only one in Canada.
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Regarding headlights, the original glacis under the extra armor plate has no holes for headlights either, some Jumbo's do have the headlight holes under the armor plate...some don't...very odd