Green’s Dictionary of Slang

flats and sharps n.

edged weapons.

1772		Bridges Burlesque Homer (3rd edn) 278: Challenge out / The boldest bruiser to a bout / At quarter-staff or cudgel play, / Or flats or sharps, or any way.
1797		Bridges Burlesque Homer (4th edn) II 11: [as cit. 1772].
1818		W. Scott Heart of Mid-Lothian (1883) 308: I have known many a pretty lad cut short in his first summer upon the road, because he was something hasty with his flats and sharps.