Playing around with the map compare function - as suggested by Optimist on the Run
Putting my ID in the first box and nothing in the second player box
Then
when I select the 'Found by one player' option in the 'show' box - it shows just caches (active and archived) I have found and no other
and when I select 'Found by both players' - nothing appears, anywhere !
when I select the 'geocaches found by no player' (which seems very specific ) in the show box - resulting in nothing that I didn't know about in the area in question (but does populate with caches further afield (and they are ones I haven't found) - so presumably that means there is nothing more to be listed in that small area I am looking at and I have therefore identified everything that has been placed in that location, ever.
Nice