Brian et al,  First of all, it's easy to identify a 2-per-turn music
box: on the right side of the cylinder is the large gear, and around
the large gear is a groove that the stop finger rides inside.  The
cylinder stops at the end of the tune by this groove and finger.

Now, if it's a 2-per-turn, it will have two dips in the groove,
otherwise it will have only one.  Since the box is playing, you can
also start it and turn it off immediately; if it plays through the
entire cylinder before stopping it's not a 2-per-turn.  (But why
would you want one, anyway?  It only shortens the length of the airs!)
Also, most 2-per-turns have fat cylinders greater than 3" in diameter,
this particular box is only 2".

Now, as for it being a forte piano -- can you hear loud/soft?  Can
you see a difference in the pin length?  You should easily be able to
hear forte/piano, and if you don't and can't see a difference in pin
lengths, it's probably not that either.

Eliyahu Shahar