Definition: for anyone building any sort of set, there are some pieces you just know up front are going to be a challenge to get. But sometimes, there's a "hole" that remains unfilled in your set despite the fact that it JUST SHOULDN'T BE THIS HARD to find one. I just now eliminated one of my OMC's. When I got the Walking Liberty half bug, the 1941-47 short set was easy, but not so cheap in a few cases (I have pretty high grade standards). Then there's that "next stage" - the 1930's, that are available for the most part, but not dropping out of the sky exactly. That's the part I'm on. When I looked at that part of the set, there WAS one coin that I expected long ago to have nabbed, but somehow I never ran across one I liked enough. That WAS the 1936-D Walker. I FINALLY got one I liked, but it took SO long! What is YOUR "OMC"? I always assumed 1936 was a weird year at mints, with all the excessive commems then.