Junebug,
I'll share with you what "Goins Encyclopedia of Cutlery Markings" has to say about G. Ibberson;
G. IBBERSON MADE IN ENGLAND c. 1700-1988 Ibberson was at 112 to 116 Rockingham Street, Sheffeild, England from 1921 to 1942. Joseph William Iberson and William Gregory Ibberson were the owners. In 1953, they were at the Violin Works, Rockingham Street, Sheffield. They made all types of cutlery, including "Bowie" type knives. G. Ibberson used the trademarks violin and double sharp.
Below this paragraph is an image of a violin with the date 1873 below it and also the image of double sharps (looks a lot like ##)
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Your knife looks to be some sort of pliers knife if I'm looking at it correctly. Hopefully someone who knows more than me will be along soon. S-K are you out there?
Phil