As it's now mining DOGE, go to the DOGE stats page and scroll down to the "LAST 50 BLOCKS FOUND" section. The validity column will show 'Orphan' for the orphaned blocks. You can't really see very far back (again, transparency is one of this pool's problems IMO), but at one point a few days ago it was like 4 orphaned out of 10 found blocks!

Crazy, and wonder if there's a way of double checking the validity of this information. Eg. is it possible to claim a block orphaned while in fact it was not?