Answer first: "512" is not an Omega model or case reference. Omega case references use a five-part format such as 210.30.42.20.01.001, and a Seamaster 300M advertised with a "512" tag is being described with a replica batch or factory code. Treat that tag as a prompt to verify the watch on its physical details, its movement and its paperwork, not on the listing title.
What the "512" tag actually is
Replica sellers group watches by internal batch codes. Those codes are short numeric strings, and they change with each production run. They are not interchangeable with Omega references, and they never appear in Omega's own documentation.
Omega Seamaster 300M 512 Replica Watch: Buyer's Verification Guide
- Genuine format: five parts separated by dots, for example 210.30.42.20.01.001.
- Batch format: a short number such as "512", often paired with a factory name.
- Practical rule: if the seller cannot give you the five-part reference, stop.
Before you start
- A 10x loupe or a macro lens for engraving and dial text.
- Digital calipers and a gram scale.
- A set of timestamped photos from the seller, including the caseback and the lugs.
- A known-authentic example of the same reference for side-by-side comparison.
How to check a Seamaster 300M, step by step
- Ask the seller for the full five-part case reference and the serial number before you discuss price.
- Read the reference engraving on the case with the loupe and confirm the digits are crisp, even in depth and free of laser haze.
- Check that the reference on the watch matches the reference printed on the warranty card and the pictograms card.
- Weigh the watch and compare the result with an authentic example of the same reference; the case and bracelet are solid stainless steel, so large gaps in weight are a signal.
- Measure the case with calipers: the modern Seamaster 300M is 42 mm across and roughly 13.5 mm thick.
- Study the caseback hippocampus under magnification; on a genuine watch the relief is deep and sharply defined, with clean edges on the tail and fins.
- Inspect the dial text and the applied logo; check letter spacing, the finish on the indices and the alignment of the date window with the frame.
- Check the date font and the position of the numeral in the window, then cycle the date through several days.
- Rotate the bezel through a full turn and count 120 clicks; the action should be firm, with no back play and no scraping.
- Unscrew the helium escape valve at 10 o'clock and confirm the threads engage and the crown seats flush.
- Unscrew the main crown, count the threads and confirm the stem is smooth through the winding, date and hand-setting positions.
- Look at the movement through the caseback: the balance should be free-sprung with a silicon hairspring, and the bridges should carry the arabesque finish and correct engraving, not a printed plate.
- Enter the movement number in the METAS Master Chronometer lookup; a current Seamaster 300M is certified, and no matching record is a serious problem.
- Open and close the clasp, check the stamped codes on the inside of the clasp blade and confirm the end links sit flush against the case.
- Charge the lume with a torch and compare brightness and color across the hands, indices and bezel pip.
Red flags that end the conversation
- A price far below the going rate for the reference and condition.
- Stock photos only, or a refusal to send a timestamped macro shot of the caseback.
- A "512" or similar batch tag offered in place of a proper reference.
- Serial on the case that does not match the paperwork.
- No pictograms card, no box, or papers from a different reference.
- A caseback that cannot be photographed clearly, which usually hides an engraved plate.
If the watch turns out to be fake
Stop the transaction and keep the correspondence. A counterfeit watch carries no manufacturer warranty, cannot be serviced with genuine parts, and is subject to seizure when it crosses a border. Pay for an inspection by an independent watchmaker before you send money, and treat any refusal to allow that inspection as an answer in itself.