Arnel molds were available via most US hobby shops. Actual end results may vary but do not change the fact that these items are more or less mass-produced and hobbyist-decorated. They are not antique and not desirable as the used materials often varied too (you never know what you get). Don’t expect more than a few dollars, if any.
Shown item is Arnel 668 which were actually two molds (body/lid). The body could be used together with four other molds to create a bird bath.