What are these Artist Symbols?

I have what appears to be an etching or painting of a European looking street scene, that does not have an artists signature. Instead, it has 3 stamped symbols on the bottom right corner. One symbol appears to be a Pheonix type bird (similar to a German symbol,) the other appears to be 2 crane type birds, and the other is 2 castles (like rooks in a chess set.) I don't expect anybody to know exactly what those mean, but can you tell me how to further research these symbols? Any place online? I sure don't want to trash this picture (though the wife hates it), so finding a value might change her mind.