I believe the very first was the Borchardt C93, introduced in 1894. The most commonly known early semi-auto was the Mauser "broomhandle" introduce in 1896 or the Browing M1900, introduced in 1898.
The actions operation.
0-60 usd
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.
50-100 USD
shotgun, rifle and pistol.
Yes, Coonan is one.
Check the receiver and barrel
The first commercially sucessful pistol was the Borchardt C-93. Designed in 1893 and became available in 1894. It is said to be the fore runner to the Luger P-08 as it was studied by the Luger's designer, Georg Luger.
The Colt M1911, a semiautomatic pistol invented by John Browning, was first made in 1910, and subsequently adopted into service with the United States Army in 1911.
What model?
Depending on EXACTLY what you have; 100-1000 USD
50-1000 or more depending on the specifics.