What 'vintage' means
There is no formal definition; the watch community typically uses 'vintage' for pre-1990 and 'neo-vintage' for 1990-2000. The dividing line is roughly when modern materials (sapphire crystal as standard, modern lume, sealed dive cases at 200m+ ratings) and modern movements (in-house calibres at industrial scale) became common. A 1965 Submariner is vintage; a 1985 Submariner is borderline; a 1995 Submariner is modern.
What you gain
Smaller, more elegant cases: vintage references commonly run 34-37mm; modern equivalents are often 40-43mm. If you have small wrists or prefer a dressy look, vintage often fits better. Patina: dial colour shifts, lume aging to cream, brass coming through plating; these are aesthetic features specific to vintage. Mechanical heritage: many vintage movements (Valjoux 72, Lemania 2310, Universal Genève 285) are recognised technical achievements with collector following independent of the brand. Cost: many vintage references trade well below modern equivalents.
What you risk
Authentication: vintage Rolex, Patek, AP all have well-documented fakes; even genuine watches often have replaced parts (dials, hands, bezels) that affect value enormously. Condition variability: every vintage watch is a snowflake; one example may be honest, another may have been refurbished poorly. Service cost: parts for older movements are often unavailable from manufacturers; specialist watchmakers cost more than brand service. Plan CHF 1,500-4,000 for a competent service of a vintage chronograph. Functional limitations: weak lume on tritium-era watches (post-12-year decay), 30-50m water resistance on older 'water-resistant' watches, less-accurate timekeeping.
How to do it right
Buy from established vintage dealers: Phillips, Bonhams, Sotheby's, Antiquorum (auction houses); HQ Milton, Watchsmith, Nick Hacko, Tropical Watch (online specialists). All authenticate and stand behind their pieces. Avoid eBay / Facebook for vintage: condition lies are the norm. Budget for service: figure 10-25% of purchase price as the post-purchase service investment. Start with one piece: don't build a vintage collection until you've owned and serviced one for a year and understand the genre. Read the references first: Hodinkee Vintage section, A Collected Man, and brand-specific forums all have deep reference materials.