An early 20th century antique ivory conversation tube with silk covered tubing by General Acoustics Ltd

With the ear piece in place the user would point the receiver to towards the person speaking, Because this was such an efficient conduit for sound it was a very effective ear trumpet, especially on a one to one basis. Ivory was not a commonly used for conversation tubes and this would have been an upmarket example. There are few records on General Acoustics Ltd although the address  is quite a prestigious one, see last photo. The advertisement shown (which was for a different type of hearing aid)  was from March 1936.

• From the Phisick collection