What style would you call this ring??

Dana ♥

The Centenary Diamond
as for the date, i'm not good at that sort of thing unless it is something i have previous personal experience with.

as for the style, though, i'd call that a cigar band

a concave cigar band, maybe? i don't know that i've ever seen a ring quite like that one.

Dana ♥

The Centenary Diamond
while not the same, i found one that looks a bit similar, on page 3 here:
https://www.houstonjewelry.com/catalogs/1961 Houston Jewelry Spring Summer.pdf

right hand side, called 7 Diamonds. like it would be the version of yours without a big center stone.
that catalog is from 1961.

i don't know if that would be more of what we'd consider a combo engagement/wedding ring or if at the time it would have been a cocktail ring.