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This is a very nice examlple of a well-known type of corkscrew generally called a "Farrow & Jackson".
In the Farrow & Jackson catalogue of 1896 (widely available in facsimile edition), this model is the first to be illustrated, although it is not given a name. Some others are. It was avaiable in brass or steel, although I have yet to see the steel model. They sold for 6 shillings and 6 pence which was slightly less than other mechanical corkscrews, but much more than plain T-shaped versions.
This corkscrew is in excellent condition with a pleasant patina and a full helix.
Date: c.1870 -1890
Dimensions: 6.5", 16.5 cm long