There are many styles in the Hamilton Nautilus series but the dials are always round and they always had the 505 movement. Some were stainless steel (500), others in 10K Gold Filled (400), some in 14K solid gold (200) and others in 10K Rolled Gold Plate (600).

Sadly, many of the Nautilus stainless steel examples have been sacrificed over the years to become donor watches for the more collectible asymmetric and solid gold cased electrics.

 

400 Series : Round Cased models in 10K Gold Filled Cases

Nautilus 403

As you can see, this is a pocket watch but contains the normal 505 movement and was released in 1965. However, it sold very poorly; those people in 1965 who still wanted a pocket watch, rather than wristwatch, were not the sort of people who wanted a new fangled electric watch. As a result, the 403 is very scarce and one of the hardest Hamilton Electrics to find.

I have two 403 pocket watches. My first one, bought in 2005, started as a case only; I added a 505 movement and was kindly given a spare dial from a Nautilus 602 which is similar to the dial from a 403. The second one I obtained in 2011 and is 100% correct!

Other 400 Series Nautilus

500 Series : Round Cased models in Stainless Steel Cases

600 Series : Round Cased models in 10K Rolled Gold Plate