Trying to identify Cobalt Stone with "ER" letters found on shore of Lake Michigan
(The Woodlands, TX)
Cobalt Blue Stone with
This piece of cobalt/navy sea glass was found on the shore of Lake Michigan, Near Winnetka, IL.
It has the letters "ER" on it and appears to be somewhere between cobalt and navy blue in color.
Any ideas of what the source was for this glass?