The online community of knife collectors, A Knife Family Forged in Steel
I don't know a lot about these but see a lot of them on Ebay over here in the UK , they don't sell for a lot of money here .
Some info here
They were originally an early version of a safety razor , the toothed design is to stop the razor cutting the skin .
They used disposable blades which could be sharpened a few times , I believe these blades are hard to find now .
I have just checked on Ebay and the last few over here didn't sell at all , though I believe the gold plated jobs are collectable .
They are often advertised as hair trimmers and indeed durham duplex do a version now that is sold as a pet trimmer , the firm is still in business selling various industrial blades .
I cannot add anything to John's information. Although not a knife, it is a beauty of a sharp object!