Although I probably started collecting around the same time as him, my card-collecting mentor would probaby be Mr. Phil Garry.
I imagine that 25 to 50% of my collection was once in his possession. I'm happy to know that a handful of the cards in his collection came from me at some point as well. Ironically, we've had at least a card or two change hands between us multiple times. There are a few that I'm sure he would love to get back from me.
Regardless, I am grateful for the hard work and research he put into the "rookie" checklist. Although he's migrated to Negro League memorabilia, he's still a "rookie" collector at heart.
Here's one that's changed hands a few times:
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http://imageevent.com/derekgranger
HOF "Earliest" Collection (Ideal - Indiv): 244/342 (71.4%)
1914 T330-2 Piedmont Art Stamps......: 114/119 (95.8%)
1923 V100 Willard's Chocolate............: 177/180 (98.3%)