Knickerbocker shotguns were made by one of two makers, Stateside. Crescent Fire Arms Company of Norwich, CT. (1892 to 1931) if made before 1915 or the Stevens Arms & Tool Company of Chicopee Falls, MA (1915 to 1940), if made after 1915. Made for and sold by H & D Folsom of New York City, a large wholesale sporting goods dealer. So there have been none made since 1940.
Value, Stateside runs about $150ish to $200ish US depending on condition.
Your's have outside hammers? Makes a difference as some models use flat springs the other coil springs. May not be just a spring if your's is hammerless. Cost of getting it running might be more than it's worth.
Anyway, Gunparts, Stateside, list some parts and they have a parts drawing. No exploded drawing though. Add the W's and note that Gunparts has a $35 US export fee. .gunpartscorp.com/Manufacturers/K.htm