{"overview":"The MTO 500mm f\/8 Grand Prix Brussels is a Soviet-built mirror (catadioptric) telephoto lens, designed as a compact long-focus optic for distant subjects such as wildlife, sport and surveillance. The 'Grand Prix Brussels' designation refers to the award MTO mirror lenses received at the 1958 Brussels World's Fair, and copies have circulated in M42 and other adapted mounts in the decades since.","market_narrative":"UK auction activity for this lens is thin: the only recorded hammer result in our data is £30 from November 2025, so both the range and median sit at £30 at saleroom level (these figures are wholesale auction prices, not retail). On that single data point alone it is hard to claim a firm market value in 2026, and condition, completeness of accessories and mount adaptability are likely to swing what a clean copy actually sells for.","buying_guide":"Inspect the front and rear elements and the internal mirror surfaces for fungus, haze and cleaning marks, as catadioptric optics are particularly sensitive to coating damage and central-mirror deterioration. Check that the focus helicoid turns smoothly without grease migration, look for separation or fogging in the corrector element, and confirm the mount and any adapter are intact, since worth and price on the used market depend heavily on optical clarity rather than cosmetics.","specs":"Key specifications confirmed by the supplied data: 500mm focal length, maximum aperture f\/8, branded as the MTO 'Grand Prix Brussels' variant.","faq":[{"q":"What is an MTO 500mm f\/8 Grand Prix Brussels worth today?","a":"Based on the limited UK auction data available, one recent hammer result was £30, so today a working copy is worth a modest sum at saleroom level rather than a collector premium."},{"q":"How much does an MTO 500mm f\/8 Grand Prix Brussels sell for at UK auction?","a":"The single recorded sale in our history sells for £30 hammer (excluding buyer's and seller's commission), which sets the only firm reference price we can cite."},{"q":"Is the value higher for clean, fungus-free examples?","a":"Almost certainly yes — mirror lenses lose value sharply once haze, fungus or mirror deterioration set in, so an optically clean example should command a higher price than the £30 baseline in our data."}],"confidence":35,"reasoning":"Only one verified sale and no SPECS or variant facts were provided, so pricing and technical claims are necessarily limited."}