Tortoise shell eyeglasses provide a warm, colorful contrast with the colder, though still attractive, sheen of all metal antique eyeglasses, and this material was actually part of an interesting trend with the Oxfords of the early 20th century: the emergence of masculine and feminine styles of vintage glasses rather than the unisex eyewear of the previous centuries.
This was to have important consequences for later generations' antique spectacles, also. Though the cat eye glasses of the 1950s, 1960s, and to some extent the modern day bear no resemblance to Oxfords, the idea of masculine and feminine eyewear led to the development of styles meant to be elegant and ladylike (such as cat eyes) or rugged and macho, enriching the eyeglass scene for many decades to come by encouraging development of different styles for different customers.
Metal Oxfords and the introduction of tortoise shell eyeglasses
Oxfords were initially made only with metal rims and bridges. These were usually made out of steel but many white gold, solid gold, and gold-filled examples were also crafted, thanks in part to the pre-Depression economy's vigor, which put purchasing power in wider segments of the population than had been true at any other point in history. Alloys were also used frequently.
Many of these metal Oxfords survive to this day, but there are also many tortoise shell eyeglasses in the Oxford configuration. These may be genuine tortoise shell eyeglasses, or zylonite. Zylonite became economically feasible to produce in large quantities and precise, fine shapes early in the 20th century, and was quickly adapted to Oxford frames.
Zylonite was often described as tortoise shell at the time, because it was often colored to duplicate the natural material harvested from the carapaces of luckless hawksbill sea turtles. This was not so much an attempt at deceitful advertising as the fact that both manufacturers and the public were rather casual about whether the tortoise shell was genuine or not, so “tortoise shell glasses” became a generic term to any vintage glasses whose frames vaguely resembled tortoise shell.
Tortoise shell glasses (whether natural or zylonite) of the Oxford type are usually fitted with a metal spring bridge and metal nose guards or plaquettes, since these parts required the tough springiness of metal and the small, precise moving parts made possible with metallic substances. However, they were often coated with zylonite as well to make them match the eyerims aesthetically.
Antique eyeglasses and masculinity
The production of Oxfords in the form of tortoise shell vintage eyeglasses ushered in the first major manufacturing of non-unisex eyewear on Earth. Before that time, spectacles and pince nez had been made to be worn by either sex. However, the burly, robust look of tortoise shell eyeglasses prompted men to purchase them as looking more masculine, while women, interested at the time in celebrating their femininity as something positive, preferred the more delicate, sleek look of metal-rimmed Oxfords.
The split was not total, of course. Many men still sported metal rimmed Oxfords without feeling their masculinity diminished, and some women wore tortoise shell eyeglasses just as readily. However, the emergence of male and female versions of Oxfords encouraged exploration of new fashions meant to cater to the tastes of one sex or the other.
Metal Oxfords studded with tiny diamonds appeared for female evening wear, while tortoise shell eyeglasses (either genuine or zylonite) sometimes appeared with very heavy frames which were likely designed to appeal to the more macho wearers of these vision aids.