Short answer
Calibre 4145 does not appear in the published movement catalogs of the Swiss and Japanese makers whose watches get sold with that number. The label shows up in replica and first copy listings, where it works as a grade name for the movement inside the case. When a seller writes "Calibre 4145," the number describes the replica supply chain, not the brand on the dial. Treat it as a product description, and verify the movement yourself if the claim matters to you.
Numbers in the 41xx block turn up on chronograph movements from several watch houses, which is why 4145 reads as believable at a glance. A real caliber number comes with a printed spec sheet: jewel count, beat rate, power reserve, and parts availability. A replica number usually comes with a photo and a promise.
Prerequisites
- A 10x loupe or a phone macro lens
- A caseback opener that matches the reference, or a watchmaker who owns one
- Precision screwdrivers for screwed casebacks
- A timegrapher, or a timegrapher app plus a microphone clip
- The maker's official caliber list for the reference you are comparing
How to check a movement claim
- Ask the seller for a sharp photo of the movement with the caseback removed and the rotor still in place.
- Read the engraving on the bridges and the rotor: brand mark, caliber number, jewel count, and country of origin.
- Compare that number against the maker's published caliber list for the reference.
- Place the watch on a timegrapher and record the beat rate in vibrations per hour.
- Check the reading against the spec sheet: most modern Swiss automatics run at 28,800 vph, while many replica movements run at 21,600 vph.
- Measure the power reserve by winding the watch fully, setting it down, and checking it each hour until it stops.
- Test the winding feel and each crown position, including hacking and quick-set date if the reference has them.
- Hand the watch to an independent watchmaker and ask for a written note on the movement.
Red flags in a Calibre 4145 listing
- The number 4145 is used with no brand name beside it.
- The movement photo is a stock image that appears on several seller pages.
- The listing claims a Swiss movement but lists no jewel count or beat rate.
- The price sits far under the market for the reference, with no note about grade.
- The serial number returns nothing when checked against brand records.
- The seller refuses to show the running movement on a timegrapher.
What the number tells you
A caliber number is only useful when it maps to a documented movement. If 4145 maps to nothing, the listing has told you something important about how the rest of the description was written. Use the checks above, get a watchmaker's note in writing, and decide with the movement in hand rather than the number on the page.