The Longines ladies' wristwatch with the reference number 817 is a vintage model, likely from the mid-20th century. The reference number helps identify the specific model within Longines' catalog and can be useful for collectors or enthusiasts trying to determine the exact production period, movement, and other specifications. Key Details: Reference 817: Indicates a specific line or model in Longines' catalog. These numbers are often used to track the history of a model, including movement type and case design. Manual-Winding Movement: Watches from this era, especially those with manual winding, are favored for their craftsmanship and intricate mechanics. Longines produced many highly accurate movements in the 1950s-1970s. Tonneau Case Style: This was a popular style for both men’s and women’s watches in the early 20th century, often considered elegant and timeless. Black Dial with Arabic Numerals: The use of Arabic numerals instead of Roman numerals or stick indices gives the watch a classic, legible style.