Any guesses?

This contraption was outside an antique shop in Alcester today.
I'm sure that there are lots of Blippers out there who know what it was used for. At £25 I was tempted to buy it so that I could research it a bit more.
Almost a full service today - optician for an eye test,  and then I went to get my hair cut. That's the top end seen to then. 
In the optician's the receptionist asked me my age. I told her, and she said something like "You look good on it." I replied "Thank you" and sat there looking smug. She then said "I said have you got any proof of date of birth on you?".  I got my driving licence out, on which I look about 150 - and by this time I felt it, and the smile had left my face. 
I said to the receptionist "I think it's the hearing aid place I need, not the optician."