MK.11 firstaid helmet dated 1943 with a MK.11 chinstrap unfortunatley no liner. See the military section of helmets and headgear for a more detailed descriptions of the helmet chin straps and liner marks .

MK.11 NO.2.D. First aid post 5 helmet in poor condition, it has a MK.11 chin strap and liner dated 1940 by Vero. Everett W. Vero & Co. (London).

MK.11 Casualty Station helmet made by JSS. Joseph Sankey & Sons Ltd (Bilston) dated 1941 with a MK.11 liner and a MK.111 chin strap, this one has been painted at least three times in its life the first the standard grey then blue and finally white for an Officer of some kind.

A MK.1V Cold war medical officers helmet with a MK.111 liner and A MK.1V chinstrap

Another cold war MK.1V helmet National hospital service reserve. The number one is possibly a regional number but there are no numbers on the helmets in the pictures below so may not be.