Lately I've been having trouble finding valleys I can hit with no losses so I started abandoning 2 of my lvl 10 forrests close to me, conquering and releasing untill I get a no loss valley and then conquering two low lvl valleys and then farming the forrests every 15 minutes. Got me 5 medals in a couple of hours last night. Also on that note in my experience no specific valley drops a specific medal, but lvl 10 forrests drop significantly more often. Last night I got a rose an honor and a nation all in a row from the same lvl 10 forest.