The company was founded in 1872 in Paris. It's always referred to as "A. Mattey" in advertisements and catalogs. A reference in the patent register related to a stereoscopy patent from 1903 mentions La Société Mattey père et fils, which proves that the company was run by father and son. A reference in the same register from 1913 mentions the name Albert Mattey and in 1914 Albert-Georges Mattey. So I assume that the first name of father and son were Albert and Albert-Georges.
Most French companies produced both stereoscopes and stereo cameras but Mattey only offered stereoscopes. A 1936 catalog shows a comprehensive range of stereoscopes from simple handheld viewers to advanced table top devices. The extensive catalog is remarkable because stereo photography was past its peak in the late 1920s.
They sold their devices using four trademarks emphasizing different product types or exclusivity. The trademark 8 & 9 can be found on revolving stereoscopes and the logo with the star appears on stereo graphoscopes. PMF refers to Maison Pennard & Fouquet. This renowned company was acquired by Mattey and emphasizes exclusivity. Unis France is the most well known trademark and was used for both handheld stereoscopes and advanced multiviewers. My Métascope contains a Unis France label, but the Pennard & Fouquet logo is also present inside the viewer. There're also many stereo viewers that are undoubtedly produced by the company, but do not contain any reference to one of its trademarks. The exact brand strategy of the company remains unclear.
It's certain that the company also supplied stereoscopes to other manufacturers which sold them using their own brand. I have seen an identical model of my revolving stereoscope with the 8 & 9 trademark and a dealer plate from camera manufacturer Mackenstein.
Because so little is known about the company, I love to find items that are linked to its history. The invoice below is for three Monocles no. 80 and dates from 1935. The price each is 46,80 francs, but the buyer apparently gets one for free. The accompanying cheque is signed by Mattey.