Try these sources: Numrich gunpartscorp.com
Jack First jackfirstgun.com
Bob's Gun Shop gun-parts.com
riverside arms co. split single shot gun
try looking at savage or Stevens shotgun diagrams. I found a firing pin for a 16 gauge riverside it was an old model 94 Stevens part
$75
What year was riverside, 12 gauge, single shot ,model 548 made
On the breach under the barel
Single shot, $35 - $90. Double barrel, $100 - $250.
it depends its about 1950-1970s
Riverside was an 'economy' brand used by the Stevens division of Savage in the 20's and 30's.
Riverside was a house brand name used by both Crescent and J. Stevens. The single shot model was of Crescent manufacture, and bl;ue book values can range up to about $125, depending on condition.
If it is a single-shot, $75-$150. Double barrel, $150-$300.
Around 75-100 dollars.
http://www.gun-parts.com/savageshotgun/ This one is better: http://www.e-gunparts.com/products.asp?chrMasterModel=2680zDOUBLE%20BARREL&MC=