It came in a yellow gold filled case as well as a coral (rose) gold case. The coral version is more rare and, thus, more collectible.
Both cases contained the 14/0 sized, 17 jewel 980 movement with sterling silver dials with 18K gold numerals. However, the dial colors differed between the two and the coral model has rhodium plated gold numerals with matching hands.
For whatever reason, the Essex is easily found in very worn condition but much more challenging to find in good shape. Typically the fixed lugs and the corners of the reverse really take a beating.
Since the lugs are fixed, a supple strap is really needed to bend over the looped lugs so the watch wears comfortably. A stiff strap makes the watch lay very flat on the wrist and many times you'll find the Essex with the strap under the lugs, rather than over them.
The Essex is often confused with the Wilshire, which also came with yellow and coral gold filled cases. The Wilshire is slightly wider and has flexible lugs. It also had gild dial options in addition to AGN.
I like the Essex though and locating a really nice one would make a welcome addition to any Hamilton collection.