What, exactly, is the CIP nomenclature on this box of ammunition telling us?

[Linked Image from i.ibb.co]
[Linked Image from i.ibb.co]

It occurs to me that in the era these shells were produced, I would have expected 2 3/4” CIP proof would be 1 1/4 ounce.

This is not recently procured ammunition, a friend bought them years ago and gave them to me. I should be more concerned that another hunting buddy has aged out, I know….

Best,
Ted