The Rietzschel Kosmo-Clack Stereo is an early twentieth-century German stereo camera, designed to expose paired images for three-dimensional viewing. Rietzschel was a Munich-based optical maker active before its absorption into Agfa, and the Kosmo-Clack was positioned as a compact stereo instrument for plate photography.

UK auction hammer results for the Kosmo-Clack Stereo show a very wide spread, with recorded sales ranging from £60 to £800 and only two data points to draw on. At saleroom level in today's market the value is highly condition-dependent, and completeness of the original leather case, plate holders and matched lens pair can move a clean example toward the upper end of that range while tired bodies sell for much less.