{"product_id":"chelsea-filter-oct-1951","title":"GAGB Chelsea Coloured Filter Oct 1951","description":"\u003cp class=\"p1\"\u003eThe \u003cb\u003emetal-cased Chelsea Filter\u003c\/b\u003e, such as the round example shown in your image and marked by the \u003cb\u003eGemmological Association of Great Britain\u003c\/b\u003e, represents a \u003cb\u003elater refinement\u003c\/b\u003e, introduced \u003cb\u003eafter the initial 1934 release\u003c\/b\u003e. Based on Gem-A instrument catalogues, manufacturing styles, and surviving examples, the metal enclosure is generally attributed to the \u003cb\u003epost-war period\u003c\/b\u003e, most likely \u003cb\u003elate 1940s to 1950s\u003c\/b\u003e, when Gem-A began standardising and professionalising gemological tools for teaching, laboratory, and trade use.\u003c\/p\u003e\n\u003cp class=\"p1\"\u003e\u003cmeta charset=\"utf-8\"\u003e\u003ci\u003eThe Journal of Gemmology ( October 1951)\u003c\/i\u003e contains an advertisement listing a “Chelsea Colour Filter” in a metal moulding — and mentions pricing — showing that by the 1951, GAGB (Gem-A) has started offering the filter in this mountings.\u003c\/p\u003e\n\u003cp class=\"p1\"\u003e\u003cmeta charset=\"utf-8\"\u003e\u003cspan\u003eThis is a museum archives and no unit is available for sale at this moment. \u003c\/span\u003e\u003c\/p\u003e","brand":"Gems.studio","offers":[{"title":"Default Title","offer_id":51520967442752,"sku":null,"price":0.0,"currency_code":"CAD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0963\/0397\/2672\/files\/GAGB1951_1.gif?v=1770678199","url":"https:\/\/gems.studio\/products\/chelsea-filter-oct-1951","provider":"Gems.studio","version":"1.0","type":"link"}