will have pottery books published by.....
BEWARE of "reference books" (price guides) put out by Schiffer, Collector's Books, and the like. Too many of them list the opinions of the author as to value with no basis in reality. There's usually a caveat of some sort about this in the beginning, something like, "the values printed are based on the author's experiences, actual selling prices, and/or prices paid by the author, among other things."
To illustrate, there were two books on antique typewriters published in 1997. One by Collector's Books and another by Schiffer. The CB one was written by someone the collectors regarded as a dealer looking to buy. Guess if his prices were high or low?!!! The Schiffer book was written by someone who was selling some of his collection.
As an example, one machine, a National, was valued by one author at $500, and by the other at $4000-$5000. Again, these books came out in the same year!!!
You'd probably be better off if you look for actual recent selling prices, or see if there's a concensus among several collectors on a value.
Best of luck,
Chuck