Vintage Diamond D-X Lubricating Motor Fuel porcelain sign (not authenticated)

This is a round, double-sided or single-sided metal advertising sign featuring the classic branding for Diamond D-X Lubricating Motor Fuel. The sign has a white background with a central orange diamond motif, superimposed with bold black and white block lettering that reads 'DIAMOND' across the top arc, large 'D-X' letters in the center, and 'LUBRICATING MOTOR FUEL' following the lower contour inside a black ribbon banner. There is a thin orange and black border encircling the entire piece. Pre-drilled mounting holes are visible near the top, left, and right edges, showing minor rust oxidation around the perimeters. The surface exhibits moderate weathering, edge chipping, and enamel loss consistent with vintage outdoor use and age, though the exact date of manufacture remains unverified. The identification rests primarily on the clearly legible corporate typography and logo graphics characteristic of mid-20th-century petroleum signage.

Based on what I can see in the photograph, this piece presents as a vintage porcelain sign featuring branding associated with Diamond D-X Lubricating Motor Fuel. The visual features include the classic white background, central orange diamond, black and white block typography, and a surrounding orange and black border with pre-drilled mounting holes showing minor rust oxidation and edge chipping consistent with age. However, I cannot verify the exact date of manufacture, material composition, or age from a photo alone, and physical inspection would be needed to confirm these details. My valuation is based on the assumption that the piece matches the stylistic characteristics of mid-20th-century petroleum signage. Assuming the attribution is correct, vintage petroliana signs in comparable weathered condition typically trade within the $400 to $700 range among collectors, driven by steady demand for authentic roadside advertising pieces. If the item turns out to be a modern reproduction, replica, copy, or produced 'in the style of', the market value would drop significantly, likely falling into the $50 to $150 range. To establish a reliable valuation and explore authenticity, an in-person examination by a qualified expert, detailed provenance documentation, and close inspection of the enamel finish and mounting points would be required.