This is a rare platinum eternity band with rose cut diamonds, with French hallmark for platinum ( dog head).
The ring has 21 rose cut diamonds totalling over half a carat, in different clarity from vs to i1, with some chips and inclusions, but not really visible to the eye. My guess is these are antique rose cuts into a newer band.
The band is 3.15mm wide and a size 7, weights 4 grams. Not sizeable.