One particularly rare flavor of the Milspec 1 uses bronze alloy cases instead of the usual steel. About 20 of these have been documented, all in an extremely tight serial
link range from 3200 to 3246. The
link case isn't actually bronze, but a similar-looking alloy designed to be anti-magnetic. Because of this
link rarity and likely connection to the U.S. military, these watches can command a 10 or 15 percent premium over a steel Milspec. But, it's a niche within a niche, within a niche, so you never know.