75mm M31A1B1 Recoilless

Recently I found this RCL case.
The M31A1B1 is for the HEAT round marked "M310A1"
“B1” is faint but without doubt there.

I have 2 questions:
First what is de difference between the M31A1 and the M31A1B1 case ?

Second what is the strange red marking on the white square ?

Just throwing a thought out… but I’d guess that the red markings are Hebrew letters?


I have no clue what the difference is between those cases or that red marking which does not look Hebrew to me, maybe Jon C, can confirm the marking, but I love seeing the big stuff. Great case!