10k gold, seed pearls, movable and transforming fittings, parts and compartments (for hair and photos) is typical of Victorian Jewelry 1860-1880's. You mention the ring has an adjustable band. Perhaps the ring was originally made for a child with the idea of it being able to be adjusted as the child grew; rings made for children during the 1880s is in perfect keeping with the period.
It looks like MAR has been engraved into the band, I really do not know what these letters stand for. It does not look like a trademark.
