Elgin introduced their Lord Elgin line of wrist watches in 1937. These were 21j watches, in solid gold and gold filled cases, and even platinum. The had the streamline, Art Deco style of the times, like this one, my latest acquisition.
The first Lord Elgin wristwatch movement was the 8/0 sized 531. Unlike the later tonneau-shaped 15/0 Lord Elgins, the 21 jewels in the 531 were placed the same as in a 21j pocket watch - jewelled through the center wheel (17), then the pallet and escape wheel cap-jeweled. The plates were damaskeened, unlike the rest of the 8/0 movements, which had brushed or satin finish.
The 531 was produced in 1937-1939. In 1940, it was superceded by the 556, such as drives this watch.
While the 531 had a split balance and blue steel hairspring, the 556 had a solid balance and white alloy 'Elginium' hairspring - presumably similar to Hamilton's 'Elinvar', and the plates and bridges were beveled. Elgin still damaskeened the plates of the 556.
This one dates to around 1941-42. By this time, Elgin had adopted the letter prefix for their serial numbers, and had begun stamping the grade on the movement as well. The 556 was produced right up till 1951, when it was replaced by the 680.
This watch is a Lord Elgin 'Cranbrook', from 1954. It's running a 680.
Early 680s still had the lovely damaskeening seen on the 531 and 556, but later this was dropped in favor of the satin finish seen here. This was the same finish used on almost all the 15/0 Lord Elgins.
Late in the 680's life, around 1955, the 688 was introduced, not to supercede the 680, but as a complement.
The 688 was essentially identical to the 680, but instead of the fixed balance wheel cap jewels, it had Incabloc shock protection. Elgin had introduced shock protection in their 641 series in 1950, but it was not until 1954 that they made a shock protected Lord Elgin.
This was also the last of the 8/0 movements, which had been introduced 20 years before with the 519. Millions of 8/0s were produced, many of them for the military in WWII. But I don't collect military watches, so someone else will have to blog about those!