How can i find out if a very old print is valuable? the artist is Franz Lefler, the print The marriage Dream.?

Question

i found it reversed in an old picture from my granny's house, covered by news paper dated 1954.

Answer 1

You can subscribe to ArtNet, http://www.artnet.com/artist/644605/franz-lefler.html
or ArtPrice, http://web.artprice.com/start.aspx
There are Prints being sold at Easy Art, http://en.easyart.com/art-prints/artists/Franz-Lefler-5405.html. I believe these are copyrighted reproductions but I'll let you research that.