John is buried at All Saints Cemetery, Jensen Beach, FL. He died at 375 Henry St. in Brooklyn, NY. He was born, according to notes in the Dunscombe family bible, at Klein Steinstrasse in Halleace Salle (upon the River Lache), Preussen, Thursday afternoon one o'clock 9/30/1847. There are at least three places in Germany called "Halle." The most likely one for the birthplace of John is also the largest of the three, southwest of Berlin in what was before reunification East Germany. Dunscombe bible references to Halle being in Prussia and the "Salle" (possibly the nearby river Salle) have led me to this conclusion. Following the custom of his family, he was given the geographical name: "Deutschland."
Web site www.rootsweb.com/~flmartin/AllSaints.html claims his gravestone has birth date 9/21/1848 and death date 2/6/1925.
Wedding ceremony performed by the Rev. Lucius Curtis, D.D., of Hartford, Ct. (a relative of the bride) and the Rev. Henry van Dyke, D.D., Pastor of the church (Severance, B. Frank. Genealogy and biography of the descendants of Walter Stewart of Scotland and of John Stewart who came to America in 1718 and settled in Londonderry, N.H. Greenfield, Mass. : T. Morey & Son, 1905, pg. 142). The church is now at Park Avenue and 91st Street (editor's note, Jan. 14, 2003).
Died at 375 Henry St., Brooklyn from esophogal cancer (smoker).
Requested Civil War service records from National Archives in 1993. None were found. A photograph of him appears to be in a U.S. Navy uniform from early 1865. Statements from (Cecil) Edward Dunscombe (John's grandson) also indicate John served in the Civil War.
Directory of the Iron and Steel Works of the United States and Canada, Volume 10, 1890, lists J.G. Dunscomb as Secretary of the Chrome Steel Works at the corner of Kent Avenue and Keap Street in Brooklyn. In 1892 he wrote a letter in that capacity to Thomas Edison (see exhibits).
The 1920 census has him living with his daughter-in-law, Marie Dunscombe, at 221 Gates Avenue in Brooklyn. This census makes some curious statements - that John's parents were both born in Germany (both were born in Bermuda), immigrated in 1889 (he turned 42 that year, we have photos of him in U.S. Naval uniform ca. 1860's, and we know that his father returned to the U.S. from Germany by 1860, and that he naturalized in 1898 (would it have been necessary for him to naturalize since his father was an American citizen at the time he was born?).
5'8" tall, brown hair, blue eyes (1888 passport application)
The 1875 Kansas state census indicates he was in Missouri before going to Kansas. Newspaper entries from Kansas indicate he was a prominent merchant. An 1875 issue of Harper's Weekly includes an illustration showing his store.
Notes accompanying the online diary of Abbie Bright, 1870-71, indicate John bought his store in 1872:

"There were a few houses not far from the river, then we saw no sign of life, except a prairie dog town, until we reached [the Ninnescah.] In all that distance there is no timber except a very little along the Cowskin creek. The creek has very steep banks, and I was glad when we had crossed it. A fringe of trees came into view, and we were nearing the river. The driver said we will stop at McLanes [McLean's] Ranch, and inquire for your brother. The ranch was a one room log building, where they sold provision and whiskey.[11]

11. A.C. McLean operated what was called "the Ninnescah ranch." It had originally been located by Edward Murray in the winter of 1869, but Murray left for a few months and when he returned a man named Charley Smith occupied the site and Murray turned over materials which he had gathered for a stockade ranch to him. Jacob "Dutch Jake" Swinddinger and Bob Lytle were involved to some degree but eventually McLean and George P. Russell acquired the land. For the next two years it was said to be the "rendezvous for all desperados along the boarder." J.G. Dunscomb bought them out in 1872 (see cover picture and sketch between pp. 248, 249) and they left for Bluff creek, Sumner county. McLean was later involved with Billy Brooks and was nearly lynched with him in 1874 as a suspected horse thief.--Andreas-Cutler, History of Kansas, p. 1387; Miller and Snell, Why the West Was Wild, pp. 53-57 (https://www.kshs.org/p/kansas-historical-quarterly-the-diary-of-abbie-bright-1870-1871-1/13214)