In 1970 or thereabouts they could be purchased from a wholesaler in
the United States for $12.00 to $15.00 a dozen.  I distinctly
remember that because I "accidentally" purchased two dozen of them a
few months before they became protected.  I had ordered 2 specimens,
but the supplier misread my order and sent me 2 dozen, and billed me,
so I just payed the bill and kept them.
Paul M.