U-Boat Soldbuch with red stamped "F"?

[Ian Jewison]

Here is a new item to the collection, however it has red "F" stamped on the cover and page 1 as opposed to a "U" which is common for U-Boat personnel.

Anyone any ideas what it could be? Of course it may not be WWII period but stamped later as he was D.M.E.A. and M.R.O (?) postwar!

Thanks!
Ian

[Notebaert David]

His name is also not filled in on page 1.

Maybe F stands for Funker? just a long shot.

[Ian Jewison]

His name is also not filled in on page 1

It is...I just edited it out to post.....

[Hank C.]

If he was "employed" post-war, it may have to do with the native language of whichever country he was working for. But I'm sure you already thought of that....

best
Hank