It actually is supposed to be an electronic readout that changes.  Many costumers actually have that working on their armor.  Check out this thread on TDH page on how it all supposed to work (quickest one I could find with a quick Google search).

http://www.thedentedhelmet.com/forums/s … php?t=2722

I was about to say the same thing there's a website that sells them along with a ton of other Boba stuff like the  boots with the little spikes,wookie braids,and so on. I'll try to find it again.
edit-
Found it!
http://www.tk409.com/fett.html you will have to scroll down,it's on the left side of the page.

http://www.thedentedhelmet.com/forums/s … php?t=2722

Nice Eyes!

Just a quick question.  I noticed that in the original ESB Boba has some sort of electric glowing electric thing on the left side of his chestplate.  Any ideas?  I'm just watching RotJ right now to see if it's the same.

Just another quick continuity thing.  In RotJ the lights are blinking.  Secondly the Insignia and the lights switch for a scene.  Though that was funny.

I thought it was supposed to be a ranking number from the Mandalorian days.

What if he was intended to be part robot?

Maybe he was at one point. I get the impression George Lucas couldn't make up his mind what to do with this character, Boba Fett.

Just another quick continuity thing.  In RotJ the lights are blinking.  Secondly the Insignia and the lights switch for a scene.  Though that was funny.