As tattooed rockers, tech bros and Instagram influencers pile into the tweedy world of watch collecting, prices for sought-after classics from brands like Rolex, Omega and Patek Philippe are shooting up. In some cases, they have doubled in just a couple of years.

These next-generation collectors see old timepieces not just as a subtly stylish way to dress up a T-shirt and jeans, but also as a hot new asset in their investment portfolios. In a market where stocks, bonds and real estate seem at an unsteady peak, do vintage watches present a Bitcoin-in-2017-like growth opportunity? Or are they in a Bitcoin-in-2017-like bubble?