I believe that's what was used to attached the other corner of the cape, which at the beginning was supposed to come accross the chest from where it is as we know it today. The cape covered all the front of Boba armor, as of the WHITE BOBA "McQuarrie concept", and some after that.....until someone more SMART probably said "forget the front cover, let's show ALL the details, and how Boba armor is really BEAT UP and worn!".
I could be wrong, but I have the theory that THAT specific piece was intended to be used in the left/back (where the cape attachment comes from "originally"), since in the MoM and/or AOSW exhibits, there's a metal piece, with a side or corner "BROKEN"....which I believe is THAT long stud piece was used at some point, to include the "belt Buckle attachment-looking-piece" in Fett's "ATTACHMENT AREA" in a scene in ROTJ at the sarlacc pit scene, but not quite sure.....guys, you be the judge on this one.
Just my 2¢...............Braks Buddy!!!!????