You have several resources available to you. On
this web site will be an “Ask the Experts” feature where you can submit
a picture and description of condition, etc. and you will get a
response with a range of value.  There are also reference books
available for purchase in book and antique stores or available in your
public library. Most popular are the books written by Ray Reiss about
dinnerware and art pottery.  There are also other authors who have
written about Red Wing pottery.