The Gillette Single ring was made from 1905 to 1921, and was the razor model that put Gillette on the map so to speak. It has an open comb, and is a 3 piece razor with a dial/barrel that unscrews at the bottom, this is directly connected to the elongated threaded rod attached to the cap. The outer barrel (grip) is a hollow tube made from brass, seemingly the same that was used for the later 1920's version, but not having a fitting pressed into it obviously helped to preserve more of these earlier model razors in an undamaged state.
The razor will deliver a medium to aggressive shave, and must be one of the most nimble razors ever made if you had to consider size, weight and the thin end cap. Here is a shave video of the razor in action, as expected the old blade does provide a bit of discomfort, but we all know we used the cherished moments of pain by using old blades for 'special occasions'
The razor weighs 51 grams and stand 82 mm high. This razor has great teeth, no cracks with little plate loss at the base of the razor.
These razors are out there, but always quite pricey to obtain, and you should grab one in good nick if it comes your way when the price is within your means