Roman? horn or antler? spindle whorl?

Gatty Slip: Spindle whirl? of bone, found on Sibertswold down, Kent. Formerly with Faussett coll. 1 1/2 in. diam.Spindle whorl, diam 4 cm. Greyish, probably made of horn or antler core - the porous texture of the inner part betrays it as organic. Otherwise very regular and polished as if turned in stone. So regular one might say it was Roman. Decorated with carefully graded grooves on a smoothly concave centre on both sides; edge also grooved.Possibly not from Sibertswold, but attributed to the site by Mayer card.