{"reference": {"slug": "zenith-1205sp", "brand": "Zenith", "ref": "1205SP", "model": "El Primero Prototype", "case_material": "Stainless Steel", "provenance": "extracted_from_auction_comps", "url": "https://mostexpensivewatches.net/reference/zenith-1205sp", "description": "The Zenith El Primero Prototype 1205SP is a pre-production chronograph manufactured between 1967 and 1969 during the development of the caliber 3019 PHC. Collectors prioritize this reference because it represents the earliest physical implementation of the high-frequency integrated automatic chronograph movement. The 1205SP features a 37mm stainless steel case with a screw-down caseback and a distinctive silver sunburst dial characterized by a date window at the 4:30 position and a lack of the \"El Primero\" branding found on later production models like the A384. Due to its status as a developmental prototype, production was limited to a small number of units, making it significantly rarer than standard production references. On the secondary market, these prototypes typically command prices in the mid-to-high five-figure range. A notable example sold at a 2019 Phillips auction for approximately 75,000 CHF, highlighting its historical importance as a functional testbed for the movement."}, "listing_stats": {"count": 9, "median": 7800.0, "low": 6950.0, "high": 15000.0, "brands": 1, "merchants": 1}, "listings": [{"id": "h_8379639464115", "title": "Zenith Zenith DEFY Skyline C.X Ceramic Edition (Pre-owned)", "brand": "Zenith", "model": "Zenith DEFY Skyline C.X Ceramic Edition (Pre-owned)", "reference": "—", "price_usd": 15000.0, "currency": "USD", "condition": "excellent", "box_papers": "full_set", "year": null, "case_material": "High-Tech Ceramic", "case_size_mm": 40.0, "movement": "Automatic", "complications": ["Chronograph"], "merchant_slug": "collective-horology", "merchant_name": "Collective Horology", "image_url": "https://cdn.shopify.com/s/files/1/0559/0623/8643/files/PB210230-2.jpg?v=1763862204", "detail_url": "https://mostexpensivewatches.net/listing/h_8379639464115", "buy_url": "https://mostexpensivewatches.net/out/h_8379639464115", "available": false}, {"id": "h_8386875031731", "title": "Zenith Zenith DEFY Skyline C.X Ceramic Edition (Pre-owned)", "brand": "Zenith", "model": "Zenith DEFY Skyline C.X Ceramic Edition (Pre-owned)", "reference": "—", "price_usd": 13500.0, "currency": "USD", "condition": "excellent", "box_papers": "full_set", "year": null, "case_material": "High-Tech Ceramic", "case_size_mm": 40.0, "movement": "Automatic", "complications": ["Chronograph"], "merchant_slug": "collective-horology", "merchant_name": "Collective Horology", "image_url": "https://cdn.shopify.com/s/files/1/0559/0623/8643/files/P1011937.jpg?v=1776800886", "detail_url": "https://mostexpensivewatches.net/listing/h_8386875031731", "buy_url": "https://mostexpensivewatches.net/out/h_8386875031731", "available": false}, {"id": "h_8091344011443", "title": "Zenith Zenith DEFY Skyline C.X for Collective (Sold Out)", "brand": "Zenith", "model": "Zenith DEFY Skyline C.X for Collective (Sold Out)", "reference": "—", "price_usd": 12300.0, "currency": "USD", "condition": "excellent", "box_papers": "full_set", "year": null, "case_material": "Stainless Steel", "case_size_mm": 41.0, "movement": "Automatic", "complications": [], "merchant_slug": "collective-horology", "merchant_name": "Collective Horology", "image_url": "https://cdn.shopify.com/s/files/1/0559/0623/8643/files/CXSquare.001_6c2b43db-180e-4e44-95ee-7570c4933453.jpg?v=1731953968", "detail_url": "https://mostexpensivewatches.net/listing/h_8091344011443", "buy_url": "https://mostexpensivewatches.net/out/h_8091344011443", "available": false}, {"id": "h_7004910321843", "title": "Zenith Zenith El Primero C.01 (Pre-owned) - 07/50", "brand": "Zenith", "model": "Zenith El Primero C.01 (Pre-owned) - 07/50", "reference": "—", "price_usd": 9800.0, "currency": "USD", "condition": "excellent", "box_papers": "full_set", "year": null, "case_material": "Stainless Steel", "case_size_mm": 40.0, "movement": "Automatic", "complications": ["Chronograph"], "merchant_slug": "collective-horology", "merchant_name": "Collective Horology", "image_url": "https://cdn.shopify.com/s/files/1/0559/0623/8643/products/Zenith_C01_Shop.jpg?v=1646256456", "detail_url": "https://mostexpensivewatches.net/listing/h_7004910321843", "buy_url": "https://mostexpensivewatches.net/out/h_7004910321843", "available": false}, {"id": "h_7548373041331", "title": "Zenith Zenith El Primero C.01 (Pre-owned) - 01/50", "brand": "Zenith", "model": "Zenith El Primero C.01 (Pre-owned) - 01/50", "reference": "—", "price_usd": 7800.0, "currency": "USD", "condition": "excellent", "box_papers": "full_set", "year": null, "case_material": "Stainless Steel", "case_size_mm": 40.0, "movement": "Automatic", "complications": ["Chronograph"], "merchant_slug": "collective-horology", "merchant_name": "Collective Horology", "image_url": "https://cdn.shopify.com/s/files/1/0559/0623/8643/files/Zenith_C01_Shop_b9583947-c593-48fc-9598-bbf175382986.jpg?v=1699630559", "detail_url": "https://mostexpensivewatches.net/listing/h_7548373041331", "buy_url": "https://mostexpensivewatches.net/out/h_7548373041331", "available": false}, {"id": "h_7480231723187", "title": "Zenith Zenith El Primero C.01 (Pre-owned) - 35/50", "brand": "Zenith", "model": "Zenith El Primero C.01 (Pre-owned) - 35/50", "reference": "—", "price_usd": 7600.0, "currency": "USD", "condition": "excellent", "box_papers": "full_set", "year": null, "case_material": "Stainless Steel", "case_size_mm": 40.0, "movement": "Automatic", "complications": ["Chronograph"], "merchant_slug": "collective-horology", "merchant_name": "Collective Horology", "image_url": "https://cdn.shopify.com/s/files/1/0559/0623/8643/files/Zenith_C01_Shop_b398c158-c00d-4ec4-8ab6-5872307d9307.jpg?v=1692124370", "detail_url": "https://mostexpensivewatches.net/listing/h_7480231723187", "buy_url": "https://mostexpensivewatches.net/out/h_7480231723187", "available": false}, {"id": "h_7465058828467", "title": "Zenith Zenith El Primero C.01 (Pre-owned) - 23/50", "brand": "Zenith", "model": "Zenith El Primero C.01 (Pre-owned) - 23/50", "reference": "—", "price_usd": 7500.0, "currency": "USD", "condition": "excellent", "box_papers": "full_set", "year": null, "case_material": "Stainless Steel", "case_size_mm": 40.0, "movement": "Automatic", "complications": ["Chronograph"], "merchant_slug": "collective-horology", "merchant_name": "Collective Horology", "image_url": "https://cdn.shopify.com/s/files/1/0559/0623/8643/files/Zenith_C01_Shop_04fbdfda-62d4-46f5-bfe2-f9eae30f311c.jpg?v=1689112655", "detail_url": "https://mostexpensivewatches.net/listing/h_7465058828467", "buy_url": "https://mostexpensivewatches.net/out/h_7465058828467", "available": false}, {"id": "h_7581195567283", "title": "Zenith Zenith El Primero Chronomaster C.01 (Pre-owned) - 39/50", "brand": "Zenith", "model": "Zenith El Primero Chronomaster C.01 (Pre-owned) - 39/50", "reference": "—", "price_usd": 7300.0, "currency": "USD", "condition": "excellent", "box_papers": "full_set", "year": null, "case_material": "Stainless Steel", "case_size_mm": 40.0, "movement": "Automatic", "complications": ["Chronograph"], "merchant_slug": "collective-horology", "merchant_name": "Collective Horology", "image_url": "https://cdn.shopify.com/s/files/1/0559/0623/8643/files/IMG_8679.jpg?v=1702321378", "detail_url": "https://mostexpensivewatches.net/listing/h_7581195567283", "buy_url": "https://mostexpensivewatches.net/out/h_7581195567283", "available": false}, {"id": "h_7300579295411", "title": "Zenith Zenith El Primero for Collective C.01 (Sold Out)", "brand": "Zenith", "model": "Zenith El Primero for Collective C.01 (Sold Out)", "reference": "—", "price_usd": 6950.0, "currency": "USD", "condition": "excellent", "box_papers": "full_set", "year": null, "case_material": "Stainless Steel", "case_size_mm": 40.0, "movement": "Automatic", "complications": ["Chronograph"], "merchant_slug": "collective-horology", "merchant_name": "Collective Horology", "image_url": "https://cdn.shopify.com/s/files/1/0559/0623/8643/products/Zenith-Chronomaster-El-Primero-C_01_03_2152_4061_80_R825_web.webp?v=1667877923", "detail_url": "https://mostexpensivewatches.net/listing/h_7300579295411", "buy_url": "https://mostexpensivewatches.net/out/h_7300579295411", "available": false}], "auction_lots": [{"slug": "zenith-1205sp-2015", "brand": "Zenith", "reference": "1205SP", "model": "El Primero Prototype", "case_material": "Stainless Steel", "hammer_usd": 73500, "year_sold": 2015, "venue": "Phillips Geneva", "lot_summary": "An extremely rare prototype of the El Primero featuring a triple calendar and moon phase, one of only 25 pieces produced in 1969.", "source_url": "https://www.phillips.com/detail/zenith/CH080215/154", "provenance": "ai_generated_grounded", "url": "https://mostexpensivewatches.net/auctions/zenith-1205sp-2015"}]}