Vintage man's sterling silver brush hallmarked SLB or 'S&B', most likely Samuel LeBas, an Irish silversmith.
9 inches by 1 3/4 inches by 1 3/4 inches high.
Bristles appear to be nylon.
There is a cartouche for a monogram, but nothing in the space.
Good condition with some apparent wear to wooden block holding bristles (see picture).