I really don't know where this cut comes from using the term beef belly, but it sure look darn close to a point cut off the brisket which happens to be my all time fave.
Sorry about the crappy pics and if it looks dry. I had to drive it back to work and finally got to eat after an hour or so. I've had there brisket point more times than I can count, and this was different.. He pulled out the whole piece and showed it to me. Let me taste it first. I've never seen a cut like that before..
I am sure Ye Olde Butcher Shop, Hirschs or Matador, all in the Plano area, can get you beef belly. Also, over here in FW, the Swiss Pastry Shop has been doing Wagyu Beef Bacon for a bit now - it looks amazing.
I'd either cure and smoke it like bacon OR dry brine it (just 1/2 Tbsp per pound - no curing salt and for less time than traditional curing) and rub with with a salt free rub and smoke it till it probes tender!
Brisket is basically the pectoral muscles of the steer. The "belly" is probably the short plate. This is where the skirt and flank steak comes from...although that doesn't look like either in my opinion. I think shagdog is right, that is naval plate.
Navel, not naval, you can cook plates from the Navy all year long, they never get tender.
Navel plate is the cut of beef, from around the navel of a steer. It is laced with fat. BBQ Bubba was playing with it for a bit there to make it into beef bacon. I see it ended up becoming BBQ instead. Looks great. Traditionally, it was used to make pastrami as well, preferred over the brisket for pastrami, where as, Jewish delis preferred brisket or round for corning.