Antiquerose123 - The window looks to me to be made by the copper foil technique, rather than by using lead came. This technique was developed by Tiffany at the end of the 19th century and allowed very small pieces of glass to be joined and sharply curved designs made. Self adhesive copper foil is wrapped around the edges of the cut/ground glass pieces which are assembled and then soldered together. The soldered lines are then either polished to keep the silver colour or patina is applied to colour the solder black, or in this case, copper and then polish is applied. Stained glass produced by this method is not weatherproof and can only be used if protected by a sheet of clear glass to protect it against the elements so I am guessing that your piece was for an internal window or serving hatch.
Sorry, I can't tell you how old the piece might be.
Leni - Love your window, I would buy a house for the same reason. Unfortunately my house which was built circa 1905 doesn't have any stained glass windows so i have added a few pieces of my own

I believe that the generic term of stained glass came from the silver stain applied to glass which was discovered around the beginning of 14th century. A silver nitrate solution is applied to the back of the glass and fired and gives a stain which can vary from pale lemon to a deep orange. I have taken various City and Guilds courses in Stained and Decorative glass but can't actually remember being given an accurate definition of stained glass. I tend to think of both yours and Antiquerose123's windows as stained glass and leaded lights as ones made up of lots of plain diamond shapes. I just love them all...........I need more glass :chky:
