Pretty much said exactly thing I was going to sayORIGINAL: epackage
Bennington marbles are a type of glazed clay marble. They are not very dense. The marbles are fired clay with a salt glaze on them. Benningtons are readily identifiable by both their coloring and the little 'eyes' that they have on them.These are spots where the marbles were touching each other while they were being fired, resulting in those spots being uncolored and unglazed. The term 'bennington' is actually a misnomer. There is no evidence that they were ever made in Bennington, Vermont, or that they have any lineage to the Bennington pottery that they resemble and from which they get their name. It appears that all Bennington marbles were imported from Germany.