A study of Mat­tey’s cat­a­logues reveals that the com­pa­ny offered an excep­tion­al­ly wide range of stere­o­scopes. The many dif­fer­ent types often dif­fered only mar­gin­al­ly in details or exter­nal appear­ance. This unusu­al­ly broad assort­ment can part­ly be explained by the var­i­ous acqui­si­tions made by Mat­tey. In most man­u­fac­tur­ing busi­ness­es, such acqui­si­tions are typ­i­cal­ly fol­lowed by a ratio­nal­i­sa­tion of the prod­uct range in order to sim­pli­fy pro­duc­tion process­es and reduce costs. At Mat­tey, how­ev­er, this appears not to have occurred, or only to a lim­it­ed extent.
The most plau­si­ble expla­na­tion is that Mat­tey did not pri­mar­i­ly tar­get indi­vid­ual con­sumers, but rather oper­at­ed with­in a busi­ness-to-busi­ness mar­ket. Mat­tey man­u­fac­tured stere­o­scopes for oth­er man­u­fac­tur­ers and retail­ers, who then sold the devices, some­times under their own names.
(from: Stere­oscopy History)