The top pick for sorting out a questionable Seamaster is a three-part check: a 10x loupe on the seahorse medallion, a cross-check of the reference number stamped around it, and a look at the movement under the caseback. That trio beats any single visual tell, because the fake hippocampus 2017 batches copied the outline of the seahorse well and failed on relief depth, border lettering, and what sits inside the case. This guide walks through each criterion, what it catches, what it misses, and when to walk away from a watch.
What the Hippocampus Is and Why 2017 Matters
The hippocampus is the seahorse figure Omega used on Seamaster casebacks, drawn from the Greek word for the animal. On genuine watches from the 1950s and 1960s it sits inside a circular border with text and, on many references, is struck into the metal rather than cut into it. The 2017 cluster of fakes and re-engraved casebacks showed up mostly on vintage-styled Seamaster listings and on modern re-editions sold through classifieds. Sellers pushed them as authentic vintage pieces or as high-grade replicas, and the giveaway was almost never the overall shape.
Criterion 1: Relief Depth and Edge Quality
- Pros: The fastest test. Struck medallions have soft, rounded edges and a consistent depth across the body, fin, and tail.
- Cons: Polishing, replating, and heavy wear can flatten a genuine medallion until it looks cut, so a bad result here is a prompt to keep checking, not a verdict.
Run your fingernail across the seahorse and then across the border text. On a struck emblem the two feel similar. On most 2017 fakes the seahorse is laser or CNC engraved, so it feels like a shallow scratch with a flat bottom while the border text stays deeper. Tilt the case under a lamp: genuine relief catches light along the whole curve of the tail, while engraved copies go dark in the middle of each fin and bright only at the outline.
Criterion 2: Lettering and Border Text
- Pros: Letterforms are hard to fake cheaply, and spacing errors survive even good photography.
- Cons: Genuine casebacks vary by reference and production year, so you need the specific reference to compare against.
Look at the weight of the strokes, the space between letters, and how close the text sits to the rim. Copies from this period tend to crowd the border, thicken thin strokes, and lose the small serifs on the lettering. Genuine stamps leave a slight lip of displaced metal at the edge of every character. Engraved text has clean walls and no lip.
Criterion 3: Reference Numbers and Case Finishing
- Pros: This ties the caseback to the case, the dial, and the crown, and mismatches are common on assembled watches.
- Cons: Genuine casebacks get swapped between watches over decades, so a mismatch alone is not proof of a fake medallion.
Read the reference number and compare the digit style with the medallion. If the medallion is struck and the number is engraved with a modern rotary tool, the two were not made together. Check the seam between caseback and case for a gap, a re-cut thread, or tool marks around the edge, which point to a caseback that has been opened and shaved to fit.
Criterion 4: The Movement and the Inside Face
- Pros: Decisive. Inside work is expensive to fake properly, and the inner face of the caseback often shows the truth.
- Cons: Requires a watchmaker, a caseback tool, and the seller's permission, which not every seller grants.
Ask for a movement photo before you buy. Then have the caseback removed. A genuine medallion pressed from the outside leaves a matching raised or recessed shape on the inside face. A caseback with a smooth inner face and a sharp seahorse on the outside was engraved after the fact.
How to Run the Check in Order
- Photograph the caseback straight on and at a 30 degree angle in daylight, no flash.
- Compare the seahorse proportions and the border text against a known genuine example of the same reference.
- Feel the relief with a fingernail and check the edge lip under a loupe.
- Match the reference number, dial, crown, and movement to each other.
- Have a watchmaker open the case before money changes hands.
Where the 2017 Batch Turns Up
Most listings sit in the vintage Seamaster bracket, priced below the going rate for a clean example, with soft photos that never quite show the caseback straight on. Auction sites with no returns and social media sales groups are the usual venues. If a seller refuses a caseback photo or a movement photo, treat that as your answer.
Recommendation by Buyer
If you want a wearable vintage look and know it is a replica, the medallion check matters less than the movement, so spend your effort on the inside. If you are paying authentic vintage money, insist on the full five-step check and a written return window. If you only want to avoid the 2017 batch in a single glance, learn the relief depth test first, because it eliminates most of them in under a minute.