Posted By:
Tim Newcombthat I'll try to steer back to the original poster's question, which is a good one for set collectors.
1. This one's not my white whale anymore since I finally got one (HA!), but on behalf of some or most of the Obak set collectors:
1910 Obak Frank Miller 
I would guess many of you know the story here. Yes, yes, everyone is entitled to collect in his own way, but still..... there's collecting and there's hoarding.
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2. Also a universal white whale: for the hundreds and hundreds of collectors who have ever tried to collect the W711-1 Cincinnati Reds set 
W711-1 Wes Livengood. A short print to rival any in the hobby-- has anyone ever seen it?
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3. My own current white whale. Common player, easy to find in M101-4, not a known short print, but I can't find him!
M101-5 #59 Ray Fisher