Value of a graphi arts unlimited inc Rudolf lesch fine arts division a old train written on train e w gale and son whittlesey princess royal signed coulson?

I have a picture the artist is Coulson signed in the bottom left corner of the picture. It is a picture for E.W. Gale and Son (the princess royal). The picture is in great condition. I found one website that had it at auction, it was listed as unsold. I would like to find out more about the artist, when the picture was made, where it was made at, and the value. I love the picture and the frame and really am not interested in selling or tossing it aside regardless of what I find out. But, I would like to atempt to put a value on it for insurance purposes