50-500 USD or so
$25000
50-250 or so
He used a Remington 870 Police Magnum.
probably 200-400 depending on condition
no but it will fit a mossburg 500
100-300 USD or so
Steel or Damascus barrels?
There's very few Remington things you can identify by just a serial but you got lucky ;) That is a Remington Model 1889 made in 1902. Value is greatly dependent on Condition, Condition, Condition, and Condition.
Remington does make a combo shotgun rifle, the Model SPR94.
Remington Model 11-48 (Highest value) Made from 1949 to 1968: 425,000 were made. $300 for all gauges except the 28 gauge. 300 percent for the 28 gauge.
Have not seen the term thumbcock. If your gun is a single shot Remington 1893 shotgun with a thumb lever on the left side of the frame, those sell for $150-$300, depending on condition.