I don't even know how antique this gun is but this is the most antique gun, i managed to have. Maybe it is a World War 2 designed Gun maybe it is a century old gun But i can only say, This gun was made with simple and perfect symmetry by professionals.

I got this gun from the house of an old retired police officer it was in pretty bad condition i did my best to restore it but badly i did not show the firing clip of the gun because i am not professional in shooting such a guns heaving extreme recoil. And i don't even have perfect safety instruments or products to fire this Gun so i don't want to take any risk but i am sure this gun will work great.

It fires a 12 Gauge bullet .

The recipe i used to make my gun black was:
This method is called hot bluing steel.
First you have to boil water with washing soda and put all the parts in it to degrease the gun.
Secondly take 1 kg POTASSIUM NITRATE (KNO3) and 1kg CAUSTIC SODA (NaOH) then mix both of them into 1 litter water and boil it. But make sure of your safety first. This is a highly exothermic reaction. So add ingredients slowly and mix them.
Put all parts in the recipe then let it boil till you get your desired blue-black color. Apply oil to the parts.