That's a perfect anvil. Cast steel is tough stuff, and Brooks made very good anvils. A lot of Brooks anvils are still easily identified by the distinctive shade of blue they use -- called, oddly enough, Brooks Blue by anvil aficionados.
If you don't want to paint the sides blue, I wouldn't recommend doing more than slathering some oil on the beauty. The working surfaces will get cleaned up soon enough once you put her to work and there's no need to scrub the light rust off before oiling. Can if you want, make her all pretty like, but it's not necessary for preservation's sake.
If you find the noise bothersome, squeeze a tube of silicone caulk out on the stump before you set the anvil down. Lots of caulk will squeeze out, but it will bond the two quite nicely and kill that church bell ring.
Great find. She's the perfect size for 99% of any smithing you'll find yourself likely to do, and that size is hugely popular and commands a premium price. That yours is near mint only makes it that much more valuable if you ever decide to part with it!
