Where do I find appraisers for old lithographs of famous paintings?

Question

I'm interested in finding the value of a lithograph of the painting 'Breezing Up', printed by Shorewood Press, Inc. The original painting came from the National Gallery of Art in Washington DC. I am unable to make out the name of the artist on the painting. This is in excellent condition

Answer 1

The original painting is by Winslow Homer.

What you have is an offset lithograph, produced by the thousands on huge mechanical presses (pretty much the way posters are). It has no value as a collectible or investment piece.