Welcome to the Forum. There were no model numbers for S&W before 1958 so the name is simply 357 Magnum Hand Ejector. They were made from 1935 to 1941 in the same serial number range as 44 Hand Ejectors, from serial number 45,768 to 60,000. There were 5500 Registered Magnums made, so check the frame behind the cylinder yoke for markings and let us know what you find. You may need a magnifying glass.

You have a very nice revolver there that would have been manufactured in 1935 or 1936. It could have shipped in those years or later.

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Gary
SWCA 2515