A couple of years ago I was fortunate enough to discover that the keypad on Fett's gauntlet was a Casio MQ-1 calculator.
Last week I made a second discovery.
I was determined to figure out what type of electonic chip can be seen in the keyslots on the back of the Fett helmet. To make a very long story short I learned more about IC chips than I EVER wanted to know. When that utterly failed to help me, I began using mesurements of the keyslots to determine the size of the chip and board. I had thought about the MQ-1 early on as a possibility but had dismissed it as being to small to cover the keyslots but after taking measurements I realized the MQ-1 would be JUST wide enough to cover them. I rushed home in a mad frenzy and tore my MQ-1 apart and there it was... the upper keyslot detail piece!!!!
The MQ-1 electronics board is divided into two halves. Half is dedicated to the keypad and the other half to the display. The two halves were seperated and the leftover display half was used for the keyslot detail. As you can see in the pics below, that piece is not long enough to cover all the keyslots. It appears a plain piece of plastic was used to cover the remaining slots. You can even see a defined break between the top and bottom in a few of the inside helmet shots we took at MoM. It is even possible that the entire MQ-1 board was used on the RotJ helmet but I am not sure... Just not enough good pics...
I still haven't figured out what the two greeblies at the bottom of the Jedi and Prepro helmets are but at least we have most of it covered.
Thanks for looking!
ESB Helmet at AoSW compared to MQ-1
ROTJ Helmet at MoM compared to MQ-1
Inside view of ROTJ Helmet at MoM
Another inside view of ROTJ Helmet at MoM