The Mentor Stereo-Reflex is a German-made twin-lens stereo plate camera, produced by Goltz & Breutmann of Dresden in the early 20th century. It was a specialist instrument aimed at photographers shooting paired images for stereoscopic viewing, sitting in the higher-end segment of the pre-war German plate-camera market.

With only one tracked UK auction hammer result on file — £360 in October 2019 — any sense of what a Mentor Stereo-Reflex is worth today rests on a very thin sample. That single saleroom result indicates the model trades in the low-to-mid hundreds at wholesale auction level, but a clean, fully working example with original ground glass and intact bellows could realistically sell for more, while a parts-only body would fetch considerably less.