In my experience, most clay spindle whorls from Meso- and South America can be said to be pre-Columbian—but I don't know of any efforts to actually serialize or date them.
The few modern attempts at reproducing these for sale, that I have seen, were all rather crude by comparison. You would see this at eye-level.
My assumption has been this: The authentic whorls are so common and numerous, there there is no profit in making accurate (compelling) imitations or reproductions. Added to this, the attraction to these artifacts can be limited. With exception, of course. I've seen spindle whorls that were a class above the common ones, in terms of fineness of detail—and these commanded higher prices.
I would be inclined to guess your whorls are ancient and authentic. As near as one can say, viewing a photo. Jamey