1960's Bernards Universal gramophone speed indicator disc - UK and Europe 50Hz

Original Bernards Universal gramophone speed indicator disc - in very good but aged condition
 
Here's a useful gadget if you still play records - if you have an adjustable speed turntable (Lenco etc.). Place the speed indicator disc on your gramophone turntable - view by the light of an electric lamp. When the turntable is rotating at a precise speed of 78 rpm (revs/minute) the blue spokes will appear to be stationary; at 45 rpm the red spokes and at 331/3 rpm the green spokes. This device will only work correctly in countries where the AC mains frequency is 50 Hz. (This means the UK, most of Europe etc. but not the USA)