Extremely rare Mercury Capsule Horizon Scanner manufactured by Barnes Engineering Company, measuring approximately 5.75″ tall and 5.5″ in diameter, labeled on the top, “Horizon Scanner, Serial No. 145…Part No. B4232-001, Model 13-130A-1-RT.” There is a ten-pin connector on top with a label below identifying the various functions. The upper portion is wrapped in a foil tape and has an additional short wire extending from the top. In fine condition. The scanner was incorporated into the the spacecraft to provide earth fixed reference to the Mercury astronaut in the event he had to assume manual attitude control during reentry; under nominal conditions an automatic attitude control system performed this function. An accurate determination of the horizon was considered a good human backup to orient the craft for a return from orbit should these automatic control systems fail. Consignor presumes this artifact to have been flown and de-installed from one of the Mercury capsules (supporting provenance is unavailable).