A single shot pistol, a Derringer and even a revolver are technically NOT considered semiautomatic. To be semiautomatic, the weapon would need to use the energy from a previous round to cycle the action. Revolvers use the muscle energy of the shooter's finger to revolved the chamber.
The actions operation.
0-60 usd
50-100 USD
Yes, Coonan is one.
shotgun, rifle and pistol.
Check the receiver and barrel
Depending on EXACTLY what you have; 100-1000 USD
What model?
50-1000 or more depending on the specifics.
Probably not. However some pistols can be fitted with an aftermarketlaser sight.
Often with a semiautomatic pistol, once a loaded magazine is inserted and the slide racked, you now have a pistol that is ready to fire: there is a fresh round in the chamber, the hammer (or striker) is cocked. This CAN be a dangerous situation, if the shooter isn't going to fire the weapon immediately. In the past, a person would have to CAREFULLY lower the hammer while pointing the pistol in a safe direction. If they slipped, they would fire a bullet accidentally AND their thumb would get hurt--mashed by the recoiling slide & hammer. A decocking lever prevents such accidents by LOWERING the cocked hammer to a safe position. Once utilized, if the shooter wanted to prepare the pistol for firing, they would have to: Manually recock the hammer, if the pistol were a single action only type, or, manually recock, or utilize the pistol's long Double Action trigger, if the pistol was a Double Action/Single Action type.