An interesting find from Alan Belson in France:
Found this double-knife switch on a vide-grenier (empty your loft) stall today. 5 1/2" x 2 1/2" porcelain base, one corner broken off. The sprung knives open with a strong snap action when the box-wood lever is pulled, by a helical spring on the drum axle.

Fuses, one missing, are on a red fibreboard plate, the fusewire is a low melting point metal - tin-alloy? Centre drum is hardwood- possibly lignum vitae?. I think this was used on dc, by the verdigris on one fuse post.

Possibly it had a wooden cover?. Weight 1lb 5 oz.

No makers marks at all, except the letters 'M' 'B' cast into the ceramic back, where incidentally all the fixing screws throught the porcelain have been potted in wax.