"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.
Seldom exceed 150 USD
25-100 USD
50-100 USD
I believe that King Nitro was a model name of Shapleigh Arms Co, St. Louis, MO.
The value of a Diamond Arms Company Shapleigh's King Nitro 20 gauge single shot shotgun with serial number 26129 can vary significantly based on its condition, age, and market demand. Generally, such shotguns can range from $150 to $400, with well-maintained examples or those with historical significance potentially fetching higher prices. For an accurate assessment, it's best to consult firearms appraisal experts or recent sales of similar models.
"Store brand" guns usually don't have much value. Maybe 100 USD.
Based on the serial number, your shotgun was manufactured in 1923. Without knowing the condition and other options, a value cannot be determined,
Impossible to value with just the serial number and "shotgun".
That patent date indicates it was made by Stevens/Savage. In NRA Good (won't be able to grade any higher if refinished) should be worth around $200-$250 retail. Being a 16 guage may lower the value in some parts of the country.
About $65-$75, depending on condition. Thee were low $$$ guns made by Crescent, who used about 100 different names. The Nitro Hunter was made for a chain of hardware stores.
Seldom exceed 125 USD