Stencil markings on M1 - thoughts?

[etomilitaria]

Hi all,

I have this Post-WWII Ingersoll shell with a stencil on the back. Would anyone be willing to share their thoughts on what they think this might mean?

I have had one suggestion that it might be from an Airborne training unit but I would be grateful to hear some thoughts from others.

Many thanks in advance.

All the best,
Rob.

[Tank Destroyer]

Rob,
Not sure if it will help but do you have more pictures of the helmet? Is the liner American or foreign? So many stenciled helmets will fall into the helmet pile of the unknowns.

Marty