If it was an original pre-war M-70 in 7x57 it would be worth a lot more than $700.00. As pointed out in this thread it is not an original so the price isn't that bad for a shooter, especially if it has alread been drilled and tapped for a scope. There never were very many of them made and many were returned to the factory and re-barreled to a differenct cartridge because of some unspecified problems with the 7x57's.
fwiw, 44Bore.