This month, the Swiss watchmaker Arnold and Son revealed two new style variations for its ultrathin Instrument Collection UTTE series—which was first introduced at last year’s Baselworld watch and jewelry show. Developed over the course of many years, the watches of the UTTE series (whose name is an acronym for “ultrathin tourbillon escapement”) feature a flying tourbillon movement that measures just 2.97 mm thick—making them some of the thinnest tourbillon watches on the market.

The two recent additions to…