As the story goes it was due to a request from King Juan Carlos of Spain that AP started using Tantalum in the late 1980's. The Spanish King wanted his Royal Oak in a more blued hue to the standard steel.

It is estimated the total Tantalum & 18ct rose gold RO's produced are in the low hundreds, owing to the difficulty working with such a unique and demanding material. Unlike the regular tapisserie dials, these stealthier even more brutalist Royal Oaks came with a captivating flat dial - Dacron vertical tantale; creating an impression of continuity with the straight-grained satin–brushed finish on the flat sections. 

Tantalum has many important uses because it doesn't scratch, is corrosion-resistant, and is basically hypoallergenic. In comparison to other materials Tantalum is a level above: It is as hard as the best steel alloys (~200 Vickers; 18k gold is ~135 Vickers) and on top, boosts about double the tensile strength of steel and gold.

Our pristine 33mm example is further enhanced with the integral 'Gay Freres' signed bracelet in tantalum and rose gold. Powered by AP's Cal. 2612 (Quartz), waterproof to 50m.