Washington 3 Cent Blue Stamp With Grill

I have a 3 cent blue Washington stamp (style is similar to the 1861 to 1868 rose color stamps) I can not find another stamp like it anywhere. The stamp is in beautiful shape and has a real nice grill on the back. There is a number in pencil on the back 83E-27. I have had a few people tell me its a so called proto type stamp that was probably never issued for postal use. I will try to get photos of the stamp uploaded but I do have a problem every time I try saying the image is to large. Any help on this stamp would be very much appreciated. Thanks

The E designation would be for an essay. Essays are test colors or designs that are used in the development of the stamp. They are listed in the back of the Scott specialized catalog. There are various types. Use the search function here to find out more.