This is a brand-new crystal model, made only for us here - the ‘Cevert’, named for François Cevert, who during his racing career wore a Seiko 6139-600x chronograph. Seiko produced three main variants of this crystal type. The first 6139s made in the first few months got the very early & short-lived bonded ‘V’-type crystal, where a flat crystal was bonded into a stainless steel ring. Almost immediately Seiko replaced this two-part crystal with a new all-glass flat-topped ‘Type 1 flat’ design. Seiko used these through the “proof” and “resist” periods, until the third type, a double-dome, was introduced.