Patek Philippe watches, or any other maker's watches for that matter with sapphire jewels are very rare. A few are known by Ekegrén, a few by Koehn, and another one by Patek Philippe. All were made for the American market. The most famous of all "blue sapphire" watches is the "Edward Howard" launched circa 1910 by the American company "Keystone". It was an extraordinary watch with sapphire jewels, jeweled banking pins, and Gyromax-like free-sprung balance. The watch attracted a great deal of attention and in the States was considered a marvel of modern watchmaking. In fact it was a revolutionary product, employing a gyromax-type balance decades before Patek Philippe. Its price was $350. By way of comparison, at the time 1916-17, a Ford Model T cost five dollars less: $345. It appears that Bunde & Upmeyer decided to cash in on the reputation of the "Blue Sapphire Howard" and asked Patek Philippe to make a similar watch with blue sapphires. The company, always ready to take up a challenge, obliged.