It is not a Registered Magnum. Registered Magnums had their registration number stamped on the frame under the yoke. This was done by stamping REG, then the registration number.
It is a common misconception that all 'pre-Model 27' 357 Magnum revolvers were Registered Magnums. The Registered Magnum program was relatively short lived, only about 5,224 were manufactured from 1935 until 1939. The Registered Magnums were custom guns, each one built to the specifications of the order. S&W never expected them to be high volume sellers. Despite the fact that they were produced during the height of the Depression, and were more expensive than anything else in the catalog at the time, S&W was swamped with orders. In 1939 the Registered Magnum program was discontinued and a registration number was no longer stamped onto the frame. "non-Regisered' 357 Magnums continued to be produced until 1941 when production ceased for war production contracts. The Post War 357 Magnum was reintroduced in 1946 with the modern micrometer click rear sight. In 1950 there were design changes to The 357 Magnum including the short throw hammer. None of these variants is a Registered Magnum. In 1957 the 357 Magnum was renamed the Model 27.
I have noticed a couple of things with the existing photos. The gun appears to be refinished outside of the factory because as near as I can make out the trigger and hammer are nickel plated. S&W never nickel plated hammers or triggers, they were always color case hardened, even on nickel plated guns.
The other thing I noticed is the small screw on the left side of the rear sight. This is indicative of an older gun with a small adjustment screw on either side of the rear sight. Modern micrometer sights have one large screw on the right side of the rear sight.
However, without clearer photos of both sides of the gun, taken straight on, it is impossible for me to determine the frame size, which is very important to determine exactly what model it is. The Serial Number stamped on the bottom of the butt would also be useful in determining what model it is.