It has a visible hammer (or two).
Hammerless
bands of iron were wrapped around a mandrel and hammered.
50-100 USD
Try e-gunparts.com
about $3500
You need to give serial number.
The Model 1878 was offered in 10 and 12 gauge from 1878 through 1889.
Wesson Fire Arms did. Values can range from 500-10000 USD dependig on EXACTLY what you have and how it is marked along with condition.
yes it can be hammered into place because it is a metal but non-metal can not be hammered into shape.
Hammered is a verb in that sentence.
Depends on what your shotgun is. If you have one of the older hammered shotguns (exposed hammer), you can decock them the same way you would any other firearm with an exposed hammer - you gently lower the hammer with your thumb. If you have a shotgun which doesn't have an exposed hammer, your only feasible way of going about this is to empty the magazine, be especially certain to ensure that the chamber is empty, and pull the trigger.
An element that can be hammered is called malleable.