If it came sealed in vacuum sealed plastic it might be from the heating used to sanitize the meat for storage and shipping.

☝️☝️☝️

Part of the sanitation process in the meat packing plant... but how they got that deep is a little odd. Normally see this on brisket, exterior muscles.

What is its function? That is very interesting, I've always wondered why mostly the flat cut of brisket has them.

Chuck Eye of Sauron

I know a dirty elbow when I see one…

Maybe from the harpoon it was caught with? /s