In some isolated cases, the people who put these types of cards out actually labelled them 1 of 12, 2 of 12, ..., 12 of 12. So through research, people have been able to identify the similar "series" of cards and make the appropriate (in my example) 12-card checklist.
Back in September, I requested more info about two of the Steve Yzerman "odd-ball" cards I have. (Card One / Card Two) Unfortunately, we weren't able to identify checklists for the sets that these are from, so I have a couple cards that will go undocumented on here. I have more than 2,000 other Yzerman cards to document here, so not a big deal. Maybe one day, they will get listed. Until then, oh well.
-- Dan --
Note: Please see my profile for more info regarding trading (section updated 3/4/2024). I have added a large portion of my inventory to the site, and currently have trading turned on (details are in my profile).