the two "f"s are the Glasgow mark.

However, it is interesting to note the case is double-hallmarked!

The strange "crossed M" at the top of the case is a Dublin import hallmark, and the date letter "m" indicates a date of 1927!

This would suggest the case was first hallmarked in Ireland in 1927, and then re-assayed when the watch was imported into Scotland...

Unusual... but not a great price-clincher to make it more valuable...