It is a Vanguard.
You will have to contact the Weatherby Collector's Association.
The model.
Blue Book of Gun Values
There is a limited amount of information available on the Weatherby website. See link below- and you did not give us the serial number. Shame on you.
Blue Book of Gun Values may have sn data.
No published sn data.
No published sn data.
You will have to contact Weatherby to find out.
Your description tells me that you have a custom rifle chambered in .300 Weatherby Magnum which was built on a 1903 Springfield action.The weatherby Cartridges did not come into being until the 1940,s and were only available in the Weatherby rifles of that time,It would be har to define a value for you because it is unknown how much work went into this rifle and the components used.If you can locate the gunsmith that made this rifle,i am sure he could tell you the amount spent to create it.
The serial number 4279990 is a partial serial number for this rifle. To determine the date the rifle was manufactured you need to provide a complete serial number that begins with letters.
You have listed the model number of your rifle,not the serial number.