BERGEON 4755 snap-on case-back tool. Designed for watchmakers and home repair of mechanical, automatic and quartz watches.
The BERGEON 4755 is the Swiss reference opener for snap-on case-backs. It combines a stainless lever arm with a precision tip designed to lift the case-back of a dress watch, a quartz piece or a vintage chronograph without marking the bezel or damaging the crystal gasket.
Manufactured in the Bergeon workshops in Le Locle, the 4755 has been the standard tool of professional watchmakers for decades. Its long ergonomic handle gives the leverage needed to lift even a tight snap-on case-back, while the polished tip slides into the slot without scratching the case lugs. Used in combination with a soft pad and a clean cloth, it is the safest way to inspect a case-back gasket, a crown gasket or an inner O-ring.
Use the 4755 every time you need to open a snap-on case-back: battery changes on a quartz watch, gasket replacement on a vintage diver, full service of a mechanical movement. It is particularly suited to watches sold without a notched back, where a screwdriver-style opener would slip.
Always work on a clean, well-lit bench. A soft pad protects both the bezel and the crystal gasket.
Watch gaskets exist in several elastomer families, each with its own properties. NBR (nitrile butadiene rubber) is the most common and offers good resistance to oils and ageing. FKM (also marketed as Viton) withstands higher temperatures and aggressive solvents, and is the preferred choice for professional dive watches. EPDM resists ozone and weathering and is often found on sport models. Hytrel, a thermoplastic elastomer, is used on certain Rolex and Omega references. This tool is fully compatible with all four families, provided the gasket is lubricated with a silicone grease such as Moebius 8217.
It can be safely used on Swiss makes (Rolex Submariner, Omega Seamaster, Tissot PRX, Longines HydroConquest), Japanese makes (Seiko 5, Seiko Prospex, Citizen Promaster) and German makes (Sinn, Junghans) as long as the case-back type matches the tool's purpose. For watches rated above 10 ATM, always pressure-test after every gasket service.
Keep the tool dry, in a clean drawer or its original sleeve. Wipe the metallic parts with a soft cloth after each use; if you have worked near solvents, dry the steel parts immediately to prevent corrosion. Inspect the working surface (tip, head or die) for marks or burrs every few months; small irregularities can be polished gently with a fine-grit abrasive cloth, but heavier damage requires replacement.
Avoid contact with strong acids, chlorinated cleaners and rubbing alcohol on plastic handles. Heat above 60 °C can soften polymer grips and reduce dimensional accuracy on precision blades — never leave the tool in direct sunlight or near a soldering iron.
Three errors account for the majority of damage observed in workshops: applying excessive torque (which strips the case-back notches), using the wrong tip diameter (which slips and scratches the bezel), and forgetting to replace a hardened gasket after service (which compromises water resistance even with a fresh O-ring of the wrong size). Always work under a loupe, double-check the gasket reference before ordering a replacement, and verify the seating of the case-back before closing the watch.
A final tip from the workshop: never combine a new gasket with an old, dried-out one on a multi-seal case. If the case-back gasket is replaced, also inspect the crown gasket and the crystal gasket — they age at the same rate and a single tired O-ring will let humidity in.
Bergeon tools are renowned for their dimensional precision and long service life. The 4755 is forged from a single piece of hardened steel and benefits from Bergeon's lifetime quality control. Origin: Switzerland.
Yes, provided the model has a snap-on case-back. Screw-down Omega Seamaster references need a different tool.
It is not recommended. A worn tip can be replaced with an original Bergeon spare to preserve the geometry.
Keep it in its cardboard sleeve, away from humidity, to preserve the chrome finish.
BERGEON 4755 snap-on case-back tool. Designed for watchmakers and home repair of mechanical, automatic and quartz watches.
