While I do think you were correct in sending this item to me for examination, I am unfortunately, at a total loss to try and guess at just how it may function. The head is obviously solid, and yet there is no doubt that it must contain some kind of internal storage device that allows it to create its strange effect- that is, storing and releasing (at will) a bolt of energy equivalent to that of lightning itself. Unfortunately, I can help you no further on this project, as the hammer itself has since been retrieve by its... owner. Please, Mr. Stark, in the future, while I appreciate examining other devices of this nature, make sure you're allowed to send them to me in the first place.
N. Tesla, Menlo Park
Wow, ok, the media list on my own steampunk-variety Thor's Hammer gets a bit weird. The head itself is made from a pair of industrial grade rubber flooring blocks, bondo, metal epoxy, and brass wire. The handle's a bit more traditional- wood and leather.
This piece will be available for sale after the end of this month.