Green’s Dictionary of Slang

(S.Afr.) a ‘wideawake’ hat, with a large brim.

1890		Jarrow Exp. 3 Oct. 7/1: In between roamed men on foot [...] troopers in corduroys and ‘smashers’.
1892		J.R. Couper Mixed Humanity 4: A wide-awake is called in South Africa a smasher.
1913		C. Pettman Africanderisms 451: Smasher A soft felt hat with a broad brim .