Nutmeg and mustard-ball graters

[size=150]There ought to be a difference between a nutmeg grater and a mustard-ball grater. Grateful if someone can tell me what it is.

Barry[/size]

At the risk of showing ignorance, what is a “mustard-ball grater”? Google doesn’t seem to know.

I have read that in the eighteenth century balls of dried mustard powder were kept in a personal container, similar to a nutmeg grater, and used in the same way. See Harold Newwman’s Dictionary of Silverware under mustard caster. thanks
Barry

I have never come across this concept before and can only suggest that the similarity between a nutmeg grater and a mustard ball grater was so great that we can no longer distinguish between the two categories.