I'm with Axel. If the shop doesn't know what a packer cut is, then go somewhere else.
To really confuse them, ask him if he wants you to give him the IAMPS # (Internation Assoc Meat Packers). IF there is a cut of meat, they have a # for it.
That "brown" discoloration is actually where the brisket is attached to the sternum (and if you get real technical, you can get a Left and a Right brisket)
Just trim off about 1/4 to 1/2 inch, expose fresh meat. I also cut off any HARD fat.