I would have it under "dubious"
The "L" and the "G" that's not from a brass hammer, for mine.
I cannot find a hammer that matches the KG5 date, but other CDS hammers, show a thinner ring, and thin characters.
The lip of the "G" is not so heavily designed.
Perhaps solicit info from Ceylon specialists, or society, ask whether there exists a GALLE hammer that has DAY/MONTH rather than MONTH/DAY.