The Audemars Piguet Royal Oak 66270TR is a Royal Oak model featuring a tantalum and rose gold case. It was produced sometime between 1988 and the 1990 The 66270TR features a quartz movement (caliber 2610) and a 24mm case size.

The use of tantalum in this watch is notable for a few reasons:

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Tantalum is an extremely durable material: It boasts a melting point over 3,000 degrees Celcius, is scratch-resistant, corrosion-resistant, and hypoallergenic. It is also about as hard as the best steel alloys and has double the tensile strength of steel and gold.

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Tantalum is difficult to work with: It cannot be soldered and is very hard to grind and finish, making it a challenging material for watchmakers to use.

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Tantalum Royal Oaks feature unique design elements: Many of the tantalum Royal Oak models feature a unique "Dacron vertical tantale" dial, which is a non-tapisserie dial variant. Additionally, no tantalum Royal Oaks were produced in the classic 39mm "Jumbo" case size.
Given the challenges of working with tantalum and the unique features of the 66270TR, it is considered a watch "for the connoisseur". The limited production numbers also make it a rare and desirable piece for collectors.