This is taken from the book of Household Management by Isabella Beeton ©1861
Butter-moulds, or wooden stamps for moulding fresh butter, are much used, and are made in a variety of forms and shapes. In using them, let them be kept scrupulously clean, and before the butter is pressed in, the interior should be well wetted with cold water; the butter must then be pressed in, the mould opened, and the perfect shape taken out. The butter may be then dished, and garnished with a wreath of parsley, if for a cheese course; if for breakfast, put it into an ornamental butter-dish, with a little water at the bottom, should the weather be very warm.
Here's a link to another blog Flipside Which shows a butter mold from the 19th century as well as a neat family history as it relates to that mold. Enjoy!