Keith's Mag 10 can be seen at the Cabela's store in Boise, along with many of Elmer's other firearms and memorabilia. Some sweet double and bolt action rifles, and of course a number of handguns.
Mike, I believe that the 10 gauge was chambered in a number of different chamber lengths up to 4" in the earlier years, but I'm not sure when the 2 7/8" became standardized. I used to purchase a box or two of 2 7/8" Remington rolled crimped shells per year in the early 70's, to use for duck hunting. I'd use these shells as a tune up to using my double 10 with the 3.5" shells for goose hunting.
I have seen reference to 2 1/2", 2 9/16" and others, including 2 7/8" chambered 10 gauges from the 1880's, so perhaps your model 1889 is in it's original configuration.
