A very fine discovery that one, a 1948 left-hand Winchester Model 70 that has what seems to be a custom Weatherby shop job. The stock work does look like that of Leonard Mews, and the rifle looks highly refined with Leupold scope, Super Grade floorplate, and swivels.
As a collector or a shooter:
The left conversion is a rare and value-added process.
Practically, the bolt rotation following conversion is ingenious design; presumably the Weatherby shop made the necessary adjustments to the bolt and receiver to ensure it was cammed and locked up as intended when changing handedness.
These custom arrangements are suggested to be mounted with accessories such as the Buehler short base.
In short, high-end custom rifle of high quality at an excellent price, to shoot and as a collector.