Threat meter from the pilot episode of TV series American Dad!
the needle can move freely.
print "Assem1 - Extremities.STL" in double, use a bit of cyanoacrylate to stick everything (except the needle obviously).
on the back you can put two magnets of 10mm in each magnet holes.
Print the lock upside down to avoid the use of support.
Only the needle need to be printed with support i think.