Here is a 1918 Receiving Ship Guantanamo Bay censored cover I picked up this week. I have no idea of its value.
The auxiliary 'censored' mark is new to me, I have not seen it before, no censor tape.
When this cover was post marked, Cuba has already joined the Allied forces and WWI was almost over. I do not know where the where the auxiliary 'censored' mark was applied but am assuming on the 'Receiving Ship'. I also do not know why the name of the Receiving Ship is not in teh cancel.