Rare Goodyear Rubber Comb Horse I R Comb Co 1851

I'm not really sure what this is for. It is a large hard rubber comb; I think made by Goodyear, by the printing on the back of it. The back reads: I R Comb Co Goodyear 1851. It measures 5" long and is almost 3" deep, with large teeth. I think, maybe it is meant for grooming a horse, as it has an image of a horse's head embossed on it. T's a hole on the top left, maybe to attach to a chain or some other type of holder. It looks quite old, but I don't know if the 1851 on the back is a date or other some sort of code. Interesting piece and nice, old fashioned image of horse. Thanks for your interest.