Houghton Mifflin did a series called Getting Ready to Read. The set used plastic pieces to represent various consonant sounds. The set has some interesting pieces including a king which is 3 1/2 inches tall. One of the interest aspects is some of the pieces are similar to the Marx animals. People wonder if Marx made it for Houghton Mifflin. I am incline that Ferriot Brothers did the molds and they change the animals to not upset Marx. The Houghton Mifflin deer is a mirror image of the Marx 60mm stag.
At the moment we do not have enough information on this set. Hopefully I will get a chance to do some research on this set so I can get a date of when it was offered, if Mark Hegeman does not beats me to it.