It's not real rare but it is a gun that alot of collectors look for because it's hard to find the 308's with a pre-one million serial number. There wasn't a whole lot of them made in 308 before 1960 so collectors and hunters are looking for them. The hunters look for them because they were made before the tang mounted safety was added instead of the lever safety yours has. Also it was cut checkered and not impress checkered. Alot of collectors think the quality of the Savage 99 went to crap after the 1 million mark so they try to dig up the pre 1 mil 308's all the time.

About 85% of the pre-mil 308's were model F's, yours on the other hand is a model EG and they only made about 10% of them in this model so it's reall hard to find and it draws a premium when they go up for sale. I personally wouldn't let it go for less than $750 the way the U.S. prices are on this model and caliber combo. I know it's an EG from your description and the fact that it has a 24" bbl, the F's had 22" bbl's.