Probably Crescent. They made shotguns known as "hardware store" guns for many businesses, marking them with the name of the store- such as Shapleigh Hardware.
Both 'King Nitro' and 'Central Arms Co' are trademarks of the Shapleigh Hardware Co, which was a major catalog retailer from the late 1800's well into the 20th century. The shotguns marketed under that name were made for Shapleigh by different companies, notably Davenport Firearms, Crescent, Hopkins & Allen, and Stevens. We'd have to see the shotgun to determine which manufacturer actually made the shotgun. www.countrygunsmith.net
You have already identified it as a Shapleigh's King Nitro. Shapleigh Hardware was in St Louis Missouri from the mid 19th century until the middle of the 20th. Their King Nitro guns were manufactured by W.H. Davenport and later by Stevens/Savage.
Some Enders Royal Service shotguns are Crescent Model 60's marked with Shapleigh Hardware's trade name, but some were made by other manufacturers.
The address of the Shapleigh Community Library is: 607 Shapleigh Corner Road, Shapleigh, 04076 0097
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"5000" is the Stevens model number, not a serial number. It was marked with the trade name for Shapleigh Hardware in St Louis around 1930. Value as either a decoration or a shooter would be $150-$250. A little more if like-new and a lot less if a basket-case.
That is impossible to determine without knowing the manufacturer and model of the shotgun.
Bertram Shapleigh died in 1940.
Bertram Shapleigh was born in 1871.
The phone number of the Shapleigh Community Library is: 207-636-3630.
If we had a manufacturer's name and model name or number we might be able to answer you.
I believe that King Nitro was a model name of Shapleigh Arms Co, St. Louis, MO.