Attached is picture of lamp of interest. It is a Pairpoint with shade signature "C. Durand".
How many are there? There are more than one.
How much is one worth?
If you Google Pairpoint with shade signature C. Durand you will see others for sale and some sold. I do not belong to this site, so you would have to sign up to find the sale price. I saw another lamp that looked the same that sold for $1500.00, but the picture was bad and I do not know if it was in good shape. With your computer a value is not hard to find. Prices can be all over the place though. Listings for sale might be extremely high. Sold price is more representative of true value. Condition must be excellent, but the auction houses with great reputations and wealthy customers can command higher prices than an individual without professional help. If you want a value for insurance, you should get a pretty good estimate on line.
Here is a link that might be useful: Pairpoint sold