I have two sets of (not vintage) mercury glass balls for sale.
One is a set of 3 blue-green balls
5½" x 6 ½" with a burnished metal ring.
best for a garland, bowl or table
or hung with ribbons,
rather than from an evergreen tree branch
the second is a set of smaller silver-gold balls,
3 ½" x 4 ½" also with rings.
Mercury glass, also known as silvered glass, contains neither mercury nor silver. It's actually clear glass, mold-blown into double-walled shapes and coated on the inside with a silvering formula, which is inserted though a small hole that is then sealed with a plug