In the 1986 Transformers movie there was a huge mcguffin and retcon stored in Optimus Prime's chest. Naturally, as this was 2 years after the toy's initial release, it was not
You've got the Touch! You've got the Backpack! YEAH!
screen accurate.
Until now. Kind of.
You see, during the Transformers 20th anniversary, there was a "Masterpiece Optimus Prime" released which was designed to be the penultimate version of the character from 1984, and it included a matrix of leadership which could be opened. But thats not what we're here for.
In 2010 there was an announcement that "BTS" would release an add on set for the ORIGINAL Optimus Prime to give him the matrix and some hands to open it with. It seems kind of crazy, but ok.
By the Power of Greyskull!