Stunning early 1900s solid 10k Yellow Gold ring with an approximately half-carat Old Euro cut round faceted natural Diamond (approximately F-color and SI1-clarity) accented by 4 natural Opal round cabochons. This unique size 5.5 Deco-style ring weighs approximately 3.72 grams and is in excellent condition for its age. The top of the ring measures 14 mm in diameter.

Old Euro-cut Diamonds, popular in the late 19th and early 20th centuries, are characterized by a distinct romantic charm born from their hand-cut nature. They feature a smaller table, a higher crown, and noticeably larger, chunkier facets, often with a visible "open" culet. This design was optimized to maximize the Diamond's "fire" - the dispersion of white light into spectral colors, particularly under softer, older lighting conditions, such as candlelight. In contrast, modern brilliant cuts, perfected with advanced technology and precise mathematical calculations (like those by Marcel Tolkowsky), emphasize "brilliance" - the reflection of white light - through a larger table, lower crown, and numerous smaller, precisely aligned facets. This results in a more scintillating, "disco ball" sparkle designed for optimal performance under contemporary electric lighting, with little to no visible culet.