That is what I am trying to figure out. which battleship. I think the USS Virginia BB-13 could be a possible match. The photo was taken on a large ship, and the Virginia fits the bill. He does not mention where he is docked in some letters. He does talk about his Captain in a letter, but it is hard to make out the name.
He was born in Brooklyn, Ny Sept 5, 1892-died Queens, Ny June 24, 1952. He enlisted May 24, 1915. Discharged possibly in 1920, as he married my great grandmother at the beginning of the New Year 1921.
I only have a small fraction of his letters, maybe in other ones, he talks about the places he went. I just remembered that he was also in Buenos Aires, St. Thomas (while on the SS Steel Age. Ok, so, that accounts for 1917-1918-1920; but where was he in 1915, 1916? I know he was in New England: Newport, Rhode Island, and maybe Boston?
It seems as though his early days, 1915-1917 were spent on the East Coast, and in 1920, in the deep South (Savannah/New Orleans, and South America.)
Ok, I know my great grandfather spent time on Iona Island. I've heard my family mention it before, and may have some books from that area. -So, it appears, the USS Apache (Aspinet-Y-176) Tug may be the ship he served on. The tug was called renamed in April, 1918, but my grandpa still wrote it as Apache in letters. Does this create a problem? This also matches, because the SS Steel Age was a cargo ship, as was the Apache (I think)
So, I think I'm figuring this out. 1915-1917 William Joseph Cahill serves in Navy (USS Virginia) later, from 1918-1920, he tranfers to the Merchant Marines. (USS Apache, SS Steel Age.)
Sorry for the long response. I'm just trying to figure it out.