Short answer
There is no 45mm Omega Globemaster. Omega catalogs the Constellation Globemaster in 39mm and 41mm cases. A listing that advertises a 45mm Globemaster is either a counterfeit, a fantasy build that pairs Globemaster styling with an oversized case, or a seller quoting a box measurement instead of the watch. Treat the 45mm figure as a warning sign, not a size option.
Why the 45mm number appears
Counterfeit workshops reuse one generic case for several models. A 45mm shell that looks roughly dressy gets a Globemaster dial, and the listing inherits the wrong diameter. Other sellers copy the number from a different Omega line, such as a dive watch, and never correct it. In both cases the number comes from the parts bin, not from Omega.
How to check a watch listed at 45mm
- Ask the seller for a photo of digital calipers across the case at the 3 and 9 positions, with the crown left out of the measurement.
- Compare the claimed figure with Omega's own catalog, which lists 39mm for the standard Master Chronometer and 41mm for the Annual Calendar.
- Request the thickness measurement as well. Cases built around generic movements run deeper than the genuine watch and sit high on the wrist.
- Ask for the caseback reference number and the eight-digit serial, then check both against the movement code.
- Look at the bezel. Genuine Globemaster bezels are solid gold with flutes cut sharp and even; plated copies show soft edges and uneven spacing.
- Inspect the dial text. Copies often use the wrong font weight for the Constellation name or set the date window off center.
- Ask for the Master Chronometer certificate and the pictogram card that matches the serial. Sellers of authentic stock have both.
Practical and legal risk
Counterfeit watches are illegal to import and to sell in the United States, and shipments are subject to seizure by customs. Buyers get no manufacturer warranty, no service from an authorized watchmaker, and no parts support. Resale value is close to zero because the watch cannot be authenticated. Payment disputes are hard to win when the item itself is contraband.
What to look at instead
If you want the Globemaster look, the 39mm Master Chronometer is the reference point, and the 41mm Annual Calendar is the larger option. If 45mm is your comfort size, the honest path is a different Omega line that actually ships that big, or a non-Omega dress watch built in that diameter. You keep the fit, the paperwork, and the resale value.