The metals commonly associated with modern watchmaking tend to be steel, gold and platinum, with the possible addition of some new high-tech alloys. Humble copper tends to be forgotten but in its alloyed form it crops up in the vast majority of watches. Copper and zinc make brass – and this alloy makes up the plates and wheels of most watches both antique and modern. Brass has great resistance to corrosion, is thermally stable, cheap and easy to work; making it a perennial choice. Low-cost watches use brass for the case too, although it is usually covered with gold, nickel or chrome plate.

The alloy du jour is brass’s darker sibling – bronze. Traditionally a mixture of copper and tin, this metal has been employed by humans since 3000BC for a variety of uses but until recently, rarely in watchmaking. Gerald Genta, ever the innovator, produced the first in 1998, but the current trend can be traced back to Panerai’s 2011 Luminor Submersible 1950 Bronzo. The maritime connection continued with a number of micro-brands producing bronze dive watches, but it took the metal’s adoption by the current cool kid in class –Tudor, with its Black Bay Bronze, along with a rather nice limited edition from Oris, for a new bronze age to be declared.

The pairing of bronze with the sea is a natural one as bronze is a marine-grade metal meaning that it doesn’t corrode under water; rather it develops a patina which acts as a protective coating for the metal underneath. While not retro in the watch-making sense, these bronze dive watches hark back to vintage marine equipment such as diving helmets.

It is too early to see if bronze watch cases are prone to that terror of the coin collector – ‘Bronze Disease’

Not all bronze watches are water babies, though; Genta’s original expresses the aesthetic qualities of the metal and the same could be said of Zenith’s Pilot Type XX Extra Special which uses bronze to suggest a vintage feel. 2016 novelties from Hautlence and Urwerk have more of the ‘steam-punk’ impression about them, mixing the cutting-edge with a distinctly Victorian ‘Captain Nemo-esque’ look; where brass and bronze are much more appropriate than steel or titanium. Schofield’s Bronze Beater celebrates the accumulation of patina along with dings marks and scratches as a true ‘everyday wear’ piece.

Patina is really what bronze is all about, adding to the endless discussion of dials and lume we can now debate the virtues of case patina/discolouration. The alloy of bronze that your brand chooses to use will have implications for the development of patina. Aluminium bronze as used by Tudor darkens slowly and in a limited way, while pure tin bronze allows more creativity as it darkens to the deep brown hue much beloved of sculpture collectors. Schofield kindly gives its Beater watch a head start with a secret-recipe acid treatment before sale but the internet is full of recipes and instructions for how you can colour your case. Too aggressive a treatment and you end up with touches of verdigris, the green oxide produced by copper, which may or may not be what you want. As verdigris stains, I suggest that a hint is good; totally encrusting the watch is bad and may lead to pitting of the case. (The copper crystals are coming from somewhere – your watch).

It is too early to see if bronze watch cases are prone to that terror of the coin collector – ‘Bronze Disease’. This little understood condition seems to occur when water gets into the structure of the metal combined with oxygen and chloride. Unlike verdigis, bronze disease eats away the underlying metal and if the green flakes fall onto other bronze items, it can be contagious. Sadly the only cure is to scrub away that hard-earned patina and start again; maybe the reason most nautical bronze that doesn’t live underwater is polished so lovingly by its owners.

The next Fellows watch sale is on 27 September. For more information, see fellows.co.uk