In a recent interview, Tesla CEO Elon Musk was spotted wearing a hard-to-find Japanese-made denim shirt jacket. Made by Iron Heart, the garment is cut from overdyed indigo 18oz selvedge denim and features copper snap buttons, a western yoke, welt hand pockets and twill-lined cuffs. The design takes inspiration from US Navy CPO shirts made from the late ‘30s through WWII. Standard-issue for Chief Petty Officers, the shirt-jacket hybrid featured hefty fabric (originally wool flannel) and was designed to be worn with layers to adjust to variable temperatures at sea.

Iron Heart’s parent company Works Inc was founded in 2003 by Shinichi Haraki after two decades of working in denim industry as a pattern maker and designer for Edwin. Originally designed for the motorcycling community, Iron Heart’s garments are made from heavyweight fabrics and are designed to be durable and long-lasting. The brand utilizes American cotton in its denim, which, with its long fibers, give even the most heavyweight jeans a soft feel and even look.

The hefty 18oz denim CPO shirt will function well as a light piece of outerwear for spring, as Musk wore it in the interview. While the fabric is heavier than what’s used in many other denim jackets, the design includes side seam gussets for ease of movement. Also, the denim is rinsed so the jacket won’t shrink after you wash it or wear it in the rain. Because the jacket is overdyed, it will develop a unique fade as you wear it. Iron Heart dyed the indigo denim with black sulfur dye, resulting in a very dark fabric. Over time, the black dye will fade, displaying the indigo base-layer.

Musk knows a thing or two about investments, and this CPO shirt is proof that his knowledge expands well into the realm of clothing. While not inexpensive at $425, this jacket is easily one of the best available. You can pick one up for yourself at now Self Edge — sizes are limited to S, L, 2XL and 3XL.

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