SUB 300

The no-decompression table is the model's distinguishing feature and it is replaceable

The bezel carries dive-table figures rather than a plain minute scale, and the specific table printed on it varies by period and market. Bezel inserts are consumable parts: they fade, they are damaged, and they are replaced — including with reproductions. An insert whose printing is crisp and unfaded on a case showing fifty years of wear has been replaced. That is a service or restoration finding, not a counterfeit one, and it is very common.

The reissues are close enough that photographs cannot settle the question

Doxa's modern SUB 300 reproduces the original with unusual fidelity, and the period watch is worth a large multiple of the modern one. Separate them physically: acrylic against sapphire, period case finish and wear, the movement, and the caseback markings. A period claim settled from images is not settled.

The colour name and the dial must agree

Professional is orange, Searambler silver, Sharkhunter black, Divingstar yellow, Caribbean blue. These are not nicknames; they are how Doxa catalogued the configurations. A watch offered as a Sharkhunter with an orange dial has been redialled, reassembled, or misdescribed, and which of those it is has to be established before anything else about the watch is assessed.

Synchron-era and US Divers dial signatures are period evidence

Doxa passed through several corporate structures, and dials of different periods carry different signatures — including co-branded US Divers dials for the American market. The signature is a dating fact, not decoration, and a signature inconsistent with the case and movement period indicates a replaced dial.