Vintage Sinclair Opaline Motor Oil Porcelain Button Sign

This is a circular, convex 'button' style advertising sign for Sinclair Opaline Motor Oil. The sign features the iconic Sinclair branding, characterized by a vibrant color palette of hunter green, crimson red, and off-white. The central graphic depicts the famous Sinclair Apatosaurus (commonly referred to as a Brontosaurus) in white with green outlines, set against a red circular field. Text elements include 'SINCLAIR' in a custom stylized green font, 'OPALINE MOTOR OIL' in bold white block lettering, and the slogan 'MELLOWED 80 MILLION YEARS' at the bottom edge. Physically, the piece appears to be made of heavy-gauge steel finished with a porcelain enamel coating. It measures approximately 12 to 15 inches in diameter based on visual scale. The condition shows significant signs of age and display; there is a dense network of surface crazing and fine hairline cracks, particularly across the white border and the dinosaur graphic. Noticeable 'flea bites' or small enamel chips are present along the outermost rim, which is typical for authentic porcelain signs of this era. The color saturation remains strong, though there is a slight yellowing or patina to the white sections. This style of signage was predominantly produced during the 1930s to 1950s, representing a peak era for American petroleana and roadside advertising. The lack of a visible maker's mark in the photograph suggests it may be located on the reverse or obscured by the mounting hardware.

I have examined the images of this Sinclair Opaline Motor Oil porcelain button sign, a classic piece of mid-century American petroleana. The sign features the iconic Sinclair 'Dino' graphic and the desirable 'Mellowed 80 Million Years' slogan, likely dating it to the late 1940s or 1950s. The visuals present strong color retention in the hunter green and crimson red, which is a positive factor for displayability. However, the value is significantly tempered by condition issues. The extensive 'crazing' and spider-web cracks across the surface, particularly on the white fields and the dinosaur graphic, indicate possible stress or exposure to extreme temperature fluctuations. While the 'flea bites' on the rim are standard for the era, the dense network of surface fractures detracts from the gloss and premium collector appeal. In similar recent auctions, pristine examples of this 12-to-15-inch button have fetched upwards of $1,200, while examples with heavy chipping or restoration drop below $350. This piece occupies a middle ground—authentic but heavily weathered. Crucially, authenticating porcelain signs via photographs is challenging due to the high volume of modern reproductions. While the rust patterns and crazing appear consistent with genuine age, I must note that high-quality 'fakes' often simulate this wear. A physical inspection would be required to verify the shelving of the enamel layers (where the different colors are fired separately) and to check the weight of the steel gauge. Without verifying the maker’s mark on the reverse or feeling the depth of the enamel racking, this valuation assumes the piece is an original period item.