Antique Brass Desk Lamp with Green Shade Edison Patients 250 v. 50 C.P. Bryant

I have this beautiful desk lamp with a nice green shade. The lamp has the mark Edison Patients 250 v. 50 C.P. on the socket (where the bulb goes) and the turn key style on/off switch says BRYANT. The lamp is about 30" tall and 24" wide. The base is about 8" in diameter. I think that this lamp is from the early 20th century but I am not sure. I also think it is made of brass but I am not sure. The lamp can be adjusted up and down as well as the length of how much it sticks out. If anyone could please help with some information about this piece, it would be greatly appreciated. The style of lamp? the shade style? material? maker? value? all original parts?