Found a similar lock for sale online listed as "Civil War Iron Padlock with Crossed Keys Cover Dug Richmond VA Campsite" although it sounds like the seller doesn't really know where its from exactly either (and may have added a few buzzwords to get extra hits).
The crossed keys and letter F on the cover might help identify the maker. The online listing is stated to be found in VA, so if you found yours there too, you might have a regional link. I think some really determined searching could identify this one.

Below is a pic of the lock listed online-
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