From my research the phone is most likely a Model 20T phone. It is marked “1 51 AL” on the transmitter / mouthpiece perch (where the mouthpiece and lamp attach to the base), which may or may not be a Western Electric part to accommodate the lamp kit. On the mouthpiece it says “Property of the American Bell Telephone Company” and “Patented July 9-89 Nov 17-91 Nov 1-92”. There is also a plate on the front of the mouthpiece that says "Property of American Tel and Tel Company", "337", and Patent USA 1141332315". On the base it has “Western Electric Company” and “Pat in USA Aug 16 04 Sept 13 04 Jan 26 15”. Inside the receiver cover it has the marking “706A”.
See photos for actual condition. I think you'll find it looks really sharp with the bright silver nickel plating. There are a minor surface scratches and mars, and a very minor dent on the top of the mouthpiece. The handset / receiver is in really good condition for its age with only a couple minor scratches. Included is a brass lamp shade holder.
NOTE THE LAMP SHADE SHOWN IN A PHOTO AND BULB ARE NOT INCLUDED - SHOWN AS A REPRESENTIVE SAMPLE SHADE ONLY AND TO SHOW IT WORKING.
The lamp holder will be shipped extended downwards for packing purposes. The screw on the perch will only need to be loosened and tightened again once the lamp holder it extended upright.
Feel free to ask questions or for additional photos. Enjoy this piece for your home, office or as a collector!