The Fat Lady is the hinge of the whole family: the first GMT-Master II, and the fork where the line split in two. Caliber 3085 let the hour hand set independently of the 24-hour hand for the first time, which is the entire difference between a GMT-Master and a GMT-Master II, and the case grew thicker to hold it - hence the nickname, with 'Sophia Loren' as the politer variant. It came only in steel and only with the red-and-black Coke bezel, the scheme's debut, and it introduced sapphire crystal and white gold marker surrounds to the line. Sources split its introduction between 1982 and 1983; production ended in 1988 either way, tying the 6542 for the shortest run in the family.
Its five years produced the family's cleanest collecting proposition: one case, one bezel scheme, one movement, transitional dial details for the specialists, and scarcity that is structural rather than promotional. Every Fat Lady is a Coke, but not every Coke is a Fat Lady - the later 16710 wore the bezel too, on a slimmer case that reads differently on the wrist.
The shortest-run modern GMT and the first of the II line, which makes it the family's quiet blue chip. Condition and originality do the pricing; the thick case hides polishing poorly, which is useful.
Production windows and specifications compiled from documented collector references and period catalogs, cross-checked across independent sources; manufacturer records for this era are approximate by Seiko's own account.