The name Stére­o­cy­cle refers to the suc­cess­ful stereo cam­era intro­duced in 1897 by Charles Bazin and Lucien Leroy. The com­mer­cial suc­cess of this cam­era led to the use of Stére­o­cy­cle as a trade­mark for oth­er prod­ucts mar­ket­ed by the Leroy com­pa­ny. The Stéréo­cy­cle box-type stere­o­scope was man­u­fac­tured by Mat­tey and brand­ed and sold by Leroy.
(from: Com­pendi­um of Stereoscopes)

How­ev­er, the illus­trat­ed view­er has some minor dif­fer­ences to the stan­dard box-type stere­o­scope by Mattey.

Fur­ther read­ing: Stere­oscopy His­to­ry Series — Bazin, Leroy & Guérin (A. Ruiter)