Found 2 shell casings inside the hull

[motto (RIP)]

The headstamp on the cases would indicate that they are in fact from MK Vll Ball Round. Anything other than Ball used a letter code to indicate what it was. If you look at your grenade launching blanks Rick, they should have the letter L in the headstamp.
The DA part of the headstamp indicates who they were made by. In this case it is Dominion I think which was Canadian.
If they were definitely rosette crimped, they must have been reprocessed cases but in that case should also have been re-identified.
The staining half way up the case I think is just that, a stain, if it was on both then it would mean something.
David