This is a good comment - though the PQ function does only allow a 500 mile radius - so if looking for the few caches worldwide (there are only 9 I have now found out) you would need to have some idea as to where they are in order to successfully identify them through a PQ - though my aim was to identify them all.
If not knowing where they are it would mean approx 400 PQs (to cover worldwide land mass) to pick up all. The above custom filter idea has proved successful in picking up all 9
Thanks anyway