Good Morning,
I believe I have a US 1936 Special Delivery 16c #CE2 with a double transfer in the middle portion of the stamp. Just as an example, if I were to take hand held stamper customized with my name on it and stamped roughly the same area twice... you would get a result like this...
US 1936 Special Delivery 16c #CE2 - Double Transfer Middle

US 1936 Special Delivery 16c #CE2 - Normal

Let me know what you think and thanks for looking.