Portable sledge-type induction coil with unusually long (100 cm) wooden track

Portable sledge-type induction coil with unusually long (100 cm) wooden track, made by Baird and Tatlock, London, 1900-1910. For stimulating muscle or nerve. Track is hinged in middle to fold into more manageable size. Small wire-covered induction coil mounted horizontally at one end, with sliding outer cover that slides whole length of wooden track. 2 brass terminals on sledge. Behind coil is trembler, electromagnet, and brass adjuster screw, all on brass mounts. Scale along top edge of slide.