Introduced in 1940, the Boulton was produced through 1952. It was reintroduced again in 1954 for one year. Then, in 1960, it was reintroduced again as the Boulton II and produced through 1969.
In addition, it was reintroduced a fourth time as a quartz version in today's modern Hamilton line up.
The vintage model always featured a high-end movement. Originally it was the 14/0 sized, 19 Jewel 982 movement. I suspect the 1954 model is the "Boulton B", although the catalogs don't call it that. The B model featured a 12/0 sized, 19J 753 movement. Finally, the Boulton II utilized the 22 jewel, 12/0 sized 770 movement - regarded as the best Hamilton ever made.
The only way to tell a Boulton and a Boulton B apart is to look at the movement. The inside of the cases are different to accommodate the different sized movements but the dials, hands, etc. are otherwise identical.
Boulton's typically wear extensively to the bottom of the lugs on the reverse. The key to finding a nice Boulton is to look at the back of the case... if the lugs are in good shape then everything else can be restored to "like new" condition. If the case is well worn, then the restorability is less.
Here's a close up of a 1940's Boulton.
And here's a Boulton B
The Boulton II features a refined dial, in addition to the 22 jewel 770 movement.
Here's a side-by-side comparison of all three.
The modern version is very similarly styled to the original but it's much larger. In addition, a white, stainless steel version is also available. Most watch enthusiasts turn up their noses at quartz watches so the modern version's appeal is limited.
The Boulton is surprisingly popular. Although it was made for many years and is easily found, it can still command a premium when it is in good shape. Like the Volkswagen Beetle, it has evolved with time but stayed true to it's original aesthetics and is easily recognizable.