Re: I.J. Double Action Model 1900
Welcome to the forum.
The cylinder pin is not screwed in, it's held in by the latch only. It may also be held in by rust.
I presume from your post, that the end of the cyliner pin that you would otherwise be able to pull out with your fingers is broken off. To remove it, cock the hammer and shine a light into the frame so that you can see the point at which the cylinder pin enters the frame. Try to push the cylinder pin out with a suitable punch from inside the frame. If it's not too rusty, it might come out that way. BTW, while you push out the pin, you must push in the cylinder pin release so that it can come out. If the pin is rusted in you may have to take it to a gunsmith for repair, if the revolver has any sentimental value. Otherwise, they are not worth very much money.