For a time Great Western offered their Frontier model revolver in a matte, ‘Parkerized’ finish. This term is well-known, and refers to durable, low reflection coatings on US military small arms. Parkerizing is achieved through various methods of phosphating or oxidizing. In their catalog, Great Western called their Parkerized option ‘copper plated black oxide’.
Great Western’s matte finish revolvers are seen somewhat regularly in 1955-56 production over the GW9000 – 14000 serial range (give or take). The early examples in this range look actually ‘parkerized’, while some latter examples might be bead blasted and blued to achieve the same, matte effect.
It would not be correct to understand the matte finish as a catalog upgrade selection, and it was not popular in its own right. Most of the 1955-56 lot of matte finish Frontiers are .22’s. They were almost undoubtedly built merely to furnish some amount of .22 revolvers for retail that would be price competitive with Ruger’s Single-Six. The Single-Six was by then wildly popular at its lower price point, that made possible by being available only in industrial, mid-grade blue.
Great Western discontinued the ‘matte’ finish by mid-1956, and began doing all their plain / base models in something of a satin blue that was a bit more attractive to the eye.

This target model has Great Western’s flat black parkerized finish.