I have the leather strapped version of this time piece.
Its a great piece of kit and have been baffling people for the last 3 days with it. great fun.
Recommendation 10/10.
I don't like it for such things but you can now buy them from ebay for 30 quid

. Seems to me to put such a fine trick in the hands of commonors at such a price is erroneous (heck, magical snobbery is creaping in)
I got mine from dudethatswhaticallcoolmagic as advertised on this fine forum.
Operation is simple, and works a treat.