[Sean]

Originally Posted by steve B

Topps has done that with some of the recent sets, and they are just considered as inserts, sort of part of the regular set.

While The T206 brands could all be individual sets, Burdick didn't catalog them that way. Probably because it was assumed all the fronts came with all the backs with only a handful of exceptions.

I don't have a t213 type 1, but aren't they thinner than the T206s? Between that and probably not quite figuring out the years of type 2 and type 3 I can see why those were thought of as different.

T215, I think was issued (Or not?) By a company that was not part of the same company that issued T206, so again a difference that would have put them as being different despite having the same fronts. Of course, they were probably also intended for a non-US distribution, so should have been classed as foreign cards instead of under the T designation.

T213 Type-1s are so thin that they feel like they're paper rather that cardboard. Ted Z. can explain this in much more detail.