Re: COLT D.A. 38 ?
Wilson's book says they started 1892 with 17100 and 1893 with 23500, so New Navy # 20076 would probably date to mid-1892. Colt continued to produce those guns even after the Army adopted the improved model in 1892; they did upgrade Model 1889 frames still in the factory to the new configuration, though, and those lasted until around 1894.
On the star with an I inside, note that the original post (from 2007) is about a different gun, a Navy contract gun of a later date than the one owned by LogicalSon. The star with an I inside was a Navy inspector's or sub-inspector's mark, but the name of the individual is not known. Other known Navy inspectors' marks are star/C (A. P. Casey) and star/W, also unknown.