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That revolver is made by Ruger. I think it is a GP100, if it is, it's a .357 magnum. It's too small to be a .44 or .45, those Rugers are a lot bigger than this one.

You are right, thank you @amberyooper.

Thanks. I'm not sure what model it is. If I had to guess, i'd say a .38 or .44 caliber double action revolver. Couldn't give you a brand or model unfortunatly.