In the early days of the Explorer, Rolex was unsure of the model's potential. As a result the name was affixed to a number of models not immediately recognizable as Explorers. Today the name and the look are so intimately entwined it seems out of place to apply the name to watches which were so obviously not what we would call 'Explorers'. There were two distinct variations on the theme and they seem to have been aimed at two distinct markets. The first variation was the so-called 'Air-King' Explorer [see lot 94]. The second variation on the theme are 'dress Explorers.' These were standard Oyster Perpetuals in steel or gold with white (or more rarely, black) non-Explorer dials featuring markers and hands, but signed 'Explorer' on the dials. Seen in both date and non-date forms, these watches all seem to have been sold in the North American market. The Explorer Date bears a model number 5700, previously unseen on any other Explorer (the nondate model is a model 5504, which interestingly is more often seen on Explorers with the standard dial). It seems that these watches were made in the 1950s or 1960s when Rolex was unsure if the Explorer would succeed or not, and attempted to increase the popularity of the watch by broadening the line. When the mainstream Explorer began to sell, these 'piggyback' models were withdrawn. As a result of its limited production, these models are extremely rare and are presently sought after by collectors.