I have a pair of fully-marked Hamilton 18S RR watches, a 21J 940, and a 17J 936.Both are motor barrels.I know the 940 is pretty common, but I haven't seen that many motor barrel 936's.Most I've seen don't have this marking on them.Is this one as common as its big brother, the 940? I often wonder why Hamilton came out with these fully marked 936's, at a time when 18 sizes were going by the wayside, especially those with 17 jewels, and 19 or more jewels was the railroad standard.Thanks, Ted.

The 940 Motor Barrels are much more common than the 936's. Hamilton introduced the motor barrel in the 18 size 936 and 940 in 1909. The 936 continued in production until 1914 and the 940 until 1928. The approximate numbers of the two that were produced from 1909 until the end of production were 5,000 for the 936 and 87,000 for the 940 so the 940 has a big edge in the numbers. Since the 940 was still selling well in 1909, I guess it made sense to add marketing features like the Motor Barrel to keep it going. And since the parts were interchangeable with the 936 it was probably a manufacturing cost savings to use it on the 936 also with the added benefit of the marketing boost there too.

Thanks Bob, makes sense to me!These 2 are really beautiful movements,I'm happy to have them. Take care, Ted.