However, in 1960, Hamilton introduced a redesigned version of the Boulton called the Boulton II. It was produced for nice additional years. That makes the Boulton design the longest running design. In fact, you an still purchase a new, modern version of the watch today!
The Boulton II has a lot in common with the original Boulton. First of all - they're virtually identical in size and shape. The even use the same crystal. Beyond that, the differences become significant.
The Boulton II came in a 10K yellow gold filled case as opposed to the 14K filled case in the original. The style of 14K solid gold numerals on the Boulton II's silver dial is sans-serif where the original 18K gold numerals were a serif style. The Boulton II has a simple cross hair register for the second hand as opposed to a more detailed seconds track from 20 years prior.
Of course, the biggest difference between the models is the Boulton II has the 22 jewel 770 movement tucked inside. The original Boulton had a 19 jewel 982 movement and it received the replacement, the 753 when the Boulton-B was was introduced in 1954.
I recently picked up a Boulton II project watch. It looked like it would be a "diamond in the rough" because of the beat up crystal. Just changing out the crystal would be a dramatic improvement.
The front of Bouillon's tend to show little wear, so the best way to assess a Boulton is the back of the lugs. It's not unusual to see the seams of the gold filled case but often you'll see the tips of the lugs worn down. This watch's lugs look a little worn, but not bad.
The crown on this watch appears to have been a "stone crown" - but the stone fell out of the center. I'll replace that with a proper crown during the overhaul.
The 770 is a fine movement. It's basically and upgraded version of the 12/0 movements that were introduced in the early 1950s - the 17 jewel 752 and the 19 jewel 753/754. The extra three jewels on the 22 jewel 770 are cap jewels - otherwise, the 770 shares most parts with the earlier grades.
Everything is disassembled, cleaned and dried before being reassembled. I've also got a new glass crystal to top off the restoration.
The running movement goes onto the timer to see how it's performing. The results were pretty good but the beat rate was almost 4.0ms. I hate having to adjust the beat error on watches with a fixed hair spring stud - as that's just tempting fate. However, 4.0ms is a high enough beat error to make me take on the risk of screwing up the balance by removing it and adjusting the hairspring collet.
When I first put the watch back on the timer, I ws delighted to see the two lines so close together. The closer they are, the lower the beat error... typically, that is. In this case, the lines are actually very far apart, so far that they approach each other on the other side. So the beat error is actually much worse - at 9.6ms. That means I moved the hairspring in the wrong directions.
In order to adjust the beat error, you're attempting to move the hairspring stud, relative to the impulse jewel - and thus center the impulse jewel with the pallet fork so the balance will swing equally to both sides. If it's not centered, the balance will swing further to one side than the other and the degree of difference is the beat error.
In the shot below, you can see the hairspring on the balance. The silver ball on the outermost coil is the hairspring stud. It's secured in the balance cock when the balance is installed. In order to move the stud relative the balance, I need to rotate the hairspring at the inner-most coil by rotating the brass collet that holds the spring on the balance staff.
Well, I'm moving in the right direction. The beat error is a reasonable 2.4ms. Notice the distance between the two lines. I'm going to press my luck and see if I can get it even better.
Now that the movement is running well, I'll turn my attention to prepping the new glass crystal. Glass crystals need to fit just right. The don't "snap into place"... they are held in place with UV cement. So I need to carefully sand all of the sides so that it will fit exactly into the contour of the bezel opening.
My light tent makes the dial look a little splotchy - I think that's actually just reflections from the dial, as I don't see the splotchiness in regular lighting. You can definitely see what an improvement a new crystal brings.
A new Hamilton crown is a nice finishing touch over the previous stone-crown.