This appears to be the superposed - load Rudolph Pelck rifle that was advertised in the Golden State Arms Catalog, back during the 1950's.
Rudolph Oswald Pelck was born in Posen, Germany (now Poznau, Poland) in 1827. He was educated at the University of Krakow. At age 13, he was apprenticed to learn the trade of locksmith and gunsmith. After serving a seven year apprenticeship, he sailed for America, and lived at first with the family of his older sister, who lived in Erie, Pennsylvania. One of them, Henry Jarecki, was also a gunsmith, and Pelck is believed to have worked for him, prior to moving to Freeport, Illinois, in about 1856. He operated his shop in Freeport, until his death, August 19, 1885. I have seen a number of his rifles over the years, and own three of them. I killed an Illinois whitetail buck with a Rudolph Pelck rifle, several years ago.