In London, The youngest of your Cartier brothers, Jacques, opened his boutique and inevitably moved it to its present area at 175-177 New Bond Street. Jean-Jacques was enamoured with watches, and he tirelessly intended and re-built the Tank in attempts to keep it pertinent for his progressively hip Londoner clientele, https://www.watchesworld.com/a-history-of-watch-reference-numbers/