Certina serial numbers are typically found on the case back, often engraved alongside the model reference number and caliber designation. The serial number format has varied over the brand's long history, and for vintage models, the serial number can sometimes be used to approximate the production date, though the encoding system is not as extensively documented as some other Swiss brands.
Vintage Certina watches may carry serial numbers on both the case and the movement, with the movement serial potentially providing different information than the case number. The movement caliber designation is often particularly useful, as it can indicate the era of production and the specific movement characteristics. Certina used proprietary calibers in their earlier history and has transitioned to ETA movements in the modern era under Swatch Group ownership.
Modern Certina watches feature comprehensive reference numbers on the case back that encode information about the model line, case material, dial variant, and strap type. These reference numbers, typically formatted similarly to other Swatch Group brands, can be looked up on Certina's website or through authorized dealers. For vintage models requiring dating, collector communities and specialized Swiss watch forums may be able to provide assistance based on the serial number and other markings.