Antique advice-can some body give me advice on an item i purchased today at an antiques shop.?

Have I been ripped off? Today I went to what I thought was a bonafide antiques dealer and purchased what was described as a 'old Doctor's pulse detector'. This consisted of a small, round, dark wooden container with a glass bevel, containing the carapace of a small tortoise or turtle. Connected to the carapace were a set of very small legs, together with head and a tail made of metal, each of which move independently of each other. The entire apparatus is suspended above the floor of the box on a small pedestal. With any form of movement, or indeed, when rested upon any part of the body, these body parts move. Whilst this would appear to substantiate a possible use, in retrospect, I am now finding it more and more unlikely that a medical practitioner would use such a kitsch tool in such a serious situation. Have you heard of any such thing, or is this a device that has been given a false description, in order to make the sale? Your opinion on this oddity would be gratefully received.