Made in Spain, these are the highest security form of these cuffs. The key they use is a flat multi-bit key. The double lock is of standard construction (a push pin in the side of the lock case.) Every version of these I have seen has a very tight spring on the latch; these cuffs CANNOT be "snapped" on.
Extra security features include:
The odd, non-standard key. The keyhole shape reduces the likelihood of successfully picking the lock.
A hinge-like link which reduces motion and freedom.
A star shaped wheel under the bow in the lock case which prevents shimming (by interlocking with the bow).