Author, Larry Shelton in his book "California Gunsmiths, 1850-1900" gave a full ten pages over to George Lumen Kingsley and his work in California. Shelton indicates that he arrived in California in 1851 and went to Mormon Island on the American River not too far from Folsom, well east and upriver from Sacramento. He found work in a hotel as a dish washer owing to illness from a disease contracted in Panama enroute to California.
When his health had improved, he moved to Michigan Bar up on the Consumnes River where he delivered newspapers before becoming a gold speculator He found a position as an agent with Wells Fargo & Co. After some
years he became very wealthy and in 1858 he married. The couple moved on to ranching sheep and cattle enterprises until severe weather and floods wiped them out. As a result they moved further north to Tehama County where they set themselves up in the business of big game hunting for wealthy clients aided by the assistance of local Indian friends. Leather goods, particularly buckskin gloves were in great demand, so in 1866, they moved to Red Bluff and established the Kingsley Glove Factory. Kingsley was known as perhaps one of the top five shots in the state and always had the best in firearms. In the same year he opened a gun shop near the leather factory selling the finest in telescopic rifles. Apparently he did not make rifles there but purchased shotguns from Clabrough & Brother of San Francisco and for a time rifles were made by George O. Leonard in New Hampshire. Looking to improve manufacturing/delivery time and to have more control, Kingsley talked Leonard into coming West, which he did in 1869. From this time on his relations with his partners and others who assisted him turned sour and pretty much remained that way until his death on September 18, 1890. It is highly unlikely that he ever made a rifle, but he ensured that the rifles sold under his name were the best available. The section dealing with Kingsley in Shelton's book are pp 138-147 and there are a number of good photographs of guns and various advertisements for his products. There is much more to this, but I hope this helps some to give an idea of who and what Kingsley was. You have a great rifle and it would be a good thing to pair it up with a copy of Shelton's book. Thank you for bringing it in for all to see.
Dick