For those who don't know, the Burdick Collection at the NY Metropolitan Museum of Art is being digitized and offered up online for viewing. About 20% of the cards are done so far, with more added all the time. The search function allows you to narrow down by names, ACC #, etc. It is worth checking out because there are already quite a few rare boxing cards up there.
Burdick was not infallible, BTW, and reviewing the cards online may help us understand some of the checklisting better. For example, Burdick identified this card as an N688:
I believe it is actually an N537 Little Rhody with the tobacco ad at the bottom trimmed off:
as this collection comes online it is going to be a great chance to find some rare cards and to refine the checklists.