Growing up, we frequently had a Boiled Supper. Same fixin's but instead of Corned Beef, Mom used Boneless Smoked Shoulder, aka, Pork Goodie, Cottage Ham or Daisy Ham. The football shaped shoulder comes encased in a plastic tube. You can't see what it looks like so you have to go by feel. Dad taught that, at refer temps, fat is Hard and lean Meat is Soft. When feeling the Shoulders, if hard and inflexible, Dad put it back. The soft Shoulders went in the cart.
Same goes for Brisket or Corned Beef. Firm, stiff Points are going to be Fatty. Soft, floppy Brisket tend to be lean and more tender...JJ
BTW...All passed on but 40 years ago, if you served Lean or Trimmed Meat, at a family gathering, the Host would have to endure a snarky razzing about not knowing what good meat looks like.