F65785 is within the Regimental Number Block (F64645-F66599) assigned to No. 6 District Depot. That the most that I can tell you.
"F" is No. 6 District which includes Nova Scotia and Prince Edward Island.
As the soldier carried the number throughout their wartime careers, it only indicates where and who they joined with. Transfers and Trade changes did not change their number.
I hope that is some small help to you.