The Lancaster Gem Apparatus is a 19th-century British plate camera produced by J. Lancaster & Son of Birmingham, a maker active in the late Victorian era. It belongs to the wood-and-brass plate-camera tradition and was sold as a compact apparatus for amateur photographers of the period.

Sales data for the Gem Apparatus is extremely thin, with only one UK auction hammer result on record at £3,600 in 2011, so any sense of what one is worth today rests on that single saleroom data point rather than a settled market range. Because hammer prices reflect wholesale levels achieved at auction and exclude commission, a clean, complete example with original fittings would be expected to command a premium, while incomplete or damaged examples typically sell for considerably less.