This brand new voltmeter, made by SMITHS in England (now doing business as CAERBONT Ltd.), is the perfect thing for monitoring the condition of your battery in any British car, although it will work fine in just about any car, British or otherwise, and matches the gauges used in most English cars of the 1960s and 1970s. It is guaranteed to work perfectly. It comes complete with bracket, installation instructions, and light socket.
It is also available with a black bezel for $15 more. Specify half vee (same profile as chrome bezel--beveled on inside only; looks like a shed roof in cross-section) or full vee (beveled on inside and outside; looks like a rounded gable roof in cross-section).