I don't know about every one, but of the two you mentioned I know some consider the Novelty Cutlery as Speaker's Rookie (if you count PostCards):
http://apr13.hugginsandscott.com/cgi...l?itemid=55712
For speaker there is also a E90-1. Since Speaker is a group 2 for t206 that makes his t206 a 1910. That would means that it is possible the e90-1 predates it his t206 by a year.
Zack wheat wasn't found in any other set that predates or at the same time as his t206