The Zeiss Ikon Sonnet 303 Tropen is a tropical-finish folding camera from Zeiss Ikon, the German optical group formed in 1926 from the merger of several established camera makers. Tropical ("Tropen") variants were built with teak or light-coloured wood bodies and brass fittings intended to resist humidity, and they typically command a premium over standard black-leather equivalents.

Auction evidence for this exact model is thin: the only recorded UK saleroom result we hold is a single hammer price of £400 in 2017, so today's value guide rests on that one data point rather than a price range. Tropical Zeiss Ikon folders are condition-sensitive at auction, and what a clean example sells for now depends heavily on the state of the wood, bellows and shutter — buyers should treat the £400 figure as indicative of wholesale auction level (excluding commission) rather than a retail asking price.