This conversation tube was made by Eschmann [Bros.] for Medresco (MEDical RESearch Council) and the Department of Health and Social Security in England in 1965.

Medresco hearing aids were distributed free to qualifying people by the British Health Service. Medresco hearing aids all began with the letters "OL" followed by some numbers. We know it was not 1876 because the first Medresco hearing aids were given out in July of 1948. The overall length of this conversation tube including earpiece and bell is 43". Notice that the tube gradually tapers from just over ¾" at the bell end to just under ½" at the earpiece end.