These days with the tremendous amount of knowledge and discussion about vintage cards occurring on a daily basis...to me...most of the printed data...especially regarding prices and such is very dated...not including more recent works of course! Similarly there are still many perceptions of the hobby that still maintain widespread acceptance because in the 70's -80's this is what was documented and published as the gospel.
Today...to me...valuations...perceived rarity...desirability has really become opinion...and we are all entitled to our own opinion.
This is why some consider t206 to be complete at 518...520...some 522...some 524. As anyone says...t206 is so great because you can collect it in so many ways?!
On the rare occasion you see an e97 set for sale...it is often considered complete without the sulivan, steinfeldt, nichols variations.
TO me...a set with all of the variations is a master set.