Parker's use of smokeless powder came in with the chambering of the new hammerless models in 1889. If a person looks at and measures the earlier chambers, they will notice the inner step intended for the brass cartridges. These brass cartridge cases could be loaded with black only, however, that does not mean that guns chambered for brass cartridges could be used only with brass, or for black only. If a person looks at and measures the barrel profile of Parker barrels made during the black era, they are thicker and less tapered than those made during the smokeless era. This is in keeping with the significantly greater initial pressure of black over the more progressive burning smokeless. During the 1890's, barrels became lighter and more tapered. I believe this was because the characteristics and advantages of the new smokeless powders became better known.

1895 Parker catalog:

And by 1892,many organized shoots had converted to smokeless powder and were providing the new smokeless cartridges to entered shooters.

that last posted picture is a dandy.. charlie