The main difference between the 5513 and the 5512 in the early 1960s was the chronometer grade calibre 1560 inside the 5512. The COSC testing and certificate made the 5512 more expensive to produce and sell—an ‘upmarket’ Submariner as compared the 5513. In accordance with that COSC treatment, the 5512 received 4-lines of text on the dial. Proudly proclaiming ‘Superlative Chronometer Officially Certified.’ Eventually, all Submariners would become COSC-certified and the 5512 disappeared from the catalog later that decade. Suffice it to say, finding an early 5512 is no small feat. The 5512 in our 7 December Important Watches sale at #SothebysNewYork is distinguished not only by its reference and ‘4-liner’ dial, but by its truly spectacular ‘tropical’ dial. The gilt black dial has aged to a rich, deep, brown color throughout with even patina across all its luminescent material. Thought to be a reaction to heat and the sun, tropical dials are highly prized for their uniqueness and rarity....