Launched in 1971, reference 1655 - also known as "Steve McQueen" - features one of the most unusual and immediately recognizable dial designs of the entire vintage rolex production. It can be considered an hybrid of an Explorer I and of a GMT. In fact, the 24-hour hand is derived from the GMT model, but in this case its elected function is not to indicate the time in a different time zone (and indeed the bezel is not revolving) but rather to indicate if it is day or night. This because the model was conceived to aid spelunkers in their cave-exploring activities, where long periods of time may go by without seeing sunlight, and thus making it quite possible to loose track of the nocturnal/diurnal cycle. In fact, the entire layout is thought with spelunking in mind: the abundance of luminous material and the bright orange hand - from which it derives its Italian nickname "Freccione", literally "big arrow" - are all features very useful in the low-light condition of caves, as is the very robust case construction. Finally, the hack features allows a group of explorers to perfectly synchronize their timepieces.