This is a real fun key, I saw some very nice little boxes on Ebay and wondered if it would be possible to fit a little collapsible key inside one, it can operate in or out of the box,  the box is only 7 x 3.5 x 3.5cm , and its proving quite difficult to make, it would have been easier to have just built a mini key to fit the box instead of having an extension to the handle, the handle is fitted with two pan head 4mm bolts the brass knob is also a screw driver to tighten or slacken them so the top arm extension can swivel round for stowage when not in use (below left) the bearings are micro size, and tightened with 8ba bolts, now more or less complete with knurled terminals and silver contacts and a surprisingly good action for such a tiny key.
The hand shot sets the scale actual key size 5.5 x 2 x 3cm