As I've mentioned frequently here, a major source of frustration for the player collector (and probably for the type-card collector as well) is the lack of documentation for certain areas of the hobby.  An excellent example of this problem are the team-issued cards given away at the ballparks in Japan.  Most teams have been issuing cards, often multiple sets a year, for decades now, but these represented a major gap in contemporary price guides and checklist catalogs.  Gary Engel has included a few in his books, but mainly just Orix BlueWave sets due to the inclusion of Ichiro. When I asked him about it he explained that his interests tended more toward the vintage areas of the Japanese hobby, and that with all the still-undocumented vintage issues he still had to cover, and not having the resources of the likes of Sports Collectors Digest in its prime, he didn't have the time to spare to modern team-issued sets.  Given how much effort it has taken me to simply compile and translate checklists for mainstream sets each year, I understand his point completely.