Tank armour

[Merlin]

I found a site that says that a the X tank (we'll call it X )

Hull armor: 15-30mm
Shield armor: 15mm

what does that mean???

[Bonzo]

I found a site that says that a the X tank (we'll call it X )
Hull armor: 15-30mm
Shield armor: 15mm

what does that mean???

What it probably means is thatareas of the hull thought more likely to be struck (generally the front) are 30mm thick, less vulnerable less thick, thinnest 15mm.

The shield is (if this is a tank and not an SP gun) probably a gun mantle, covering the hole in the turret where the gun comes out of and with holes for the coaxial mg and gun optics. The Gun mantle is often mounted on the gun barrel and so its weight must be accounted for in balancing the gun itself to allow proper elevation and depression, the turret to allow proper rotation on uneven terrain and the suspension so that the tank rides level. This need to balance often resulted in thinner than desired gun shields. The American M26A1Ee Super Pershing had a beefed up gun mantle that got the first two right, but not the suspension so it was nose heavy and rode accordingly.