I joined in July and am delighted with the forum. I see you are interested in microscopes.
I have a question....during demolition of a hopsital my son found a very old microscope in the building. I researched this item and found it to be a Duboscq Colorimeter, made in the late 1800's. They became obsolete in 1960. Replaced by the modern version.
I found the Duboscq Colorimeter in a site at the Humboldt University Scientific Museum.
In my search I have not found a site that gives the value of this meter. Do you have knowledge of this product and the value? Or send me to a site that has this info. I am sending a photo from the website so you will have a visual of the meter. The only difference of the one we found and the photo is ours has an electric cord attached to it. I don't know what that means....I appreciate your help.