I suspect the source of the 1882 death date is a photo of the Oak Hill Cemetery monument. In a photo I took of the monument many years ago, it looks like 1882, or even 1832, but in fact he died 5/26/1892 according to his death certificate. I intend to make a trip to the cemetery to get a better photo.

His first son William Henderson Moses is not listed. He is not buried at the monument site, but a few feet away in Lot 515E
b. 9/8/1859 Cleveland, OH
d. 11/12/1931 Wash. DC
m. 10/4/1886 NY, NY
Estelle Maloy
b. 1/20/1862 NY, NY
d. 2/25/1946 Wash. DC

His second son, Henry Clarke Hill Moses is not listed. He is not buried in Oak Hill, but in Harleigh Cemetery, Camden, NJ.
b. 2/4/1869 Wash. DC
d. 12/14/1928 Wash. DC
m. 10/5/1899 Haddonfield, NJ
Edith Mann
b. 11/27/1876 Philadelphia, PA
d. 11/27/1974 Bethesda, MD