The picture of my Mother, my brother and I on a snowmobile has “Jun 75” stamped on the bottom of it. It was taken on a frozen pond south of the house where we grew up.
It was not taken in June of 1975. That was the month the picture was developed. There was some time where developed photographs had the month and year of development stamped on them.
At the time this was common knowledge. There did not need to be a warning phrase “this is when the photograph was developed.”
Documents often contain a variety of dates–execution, acknowledgement, recording, returning, etc.–that may be spelled out explicitly on that document. Sometimes those dates are not explained but remember that any piece of information on a record–especially if it is seemingly just randomly dropped there–may not mean what you think it means.
June of 1975 probably was when Mom had filled the roll of film and wanted to get it developed. That’s what it means.