The number 10 “printed” on a piece of film and adhered to the lower left corner of a 4×5 film holder, that is not coincidentally numbered 10.

AF 56. Corner of Weegee print.

In the corner of some full frame Weegee prints (easily seen on some of the “portfolio” prints) there is an AF, Arthur Fellig, and a number. Usually it is inverted, interestingly not on the above print.
Perhaps these AFs were constructed like the above 10. And used from approximately 1942-1944. (More exact dates will be forthcoming.)
During this time period, it’s common to see other PM Daily photographers’ initials “written” on the corner of their prints. And many other press photographers have similar initials, names, and/or photo agencies (ACME, etc.) “written” on their negatives and prints…

(All images except for the film holder are screen shots from the great Met. Museum website.)

If the above AF thoughts are true, then it’s a useful way to date Weegee photos. And further proof that the photo “Summer on the Upper West Side,” often called “Summer on the Lower East Side, ca. 1937”, was made later, around 1944…

(To be continued…)