Pattern 23 is Strand's classic Baby Mirror Spotlight (profile spot with gate/masks) engineered for precise beam shaping via fixed aperture masks. It uses front and rear reflectors to project through a gate with four fixed masks, plus optional iris diaphragm, adjustable straight-edge masks, and four-sided shutters. A 500 W tungsten lamp (T/1 or T/17) in a P28s lampholder powers multiple objective lens configurations, delivering beam angles roughly 17°–30° and a throw near 8 m across Patt. 23 variants.