I have an early size 6 American watch co royal that has no serial number on it.it must have been missed at the factory.i have had it completely apart and there are no numbers anywhere on the movement.i have about a dozen of the same style movements and they are all stamped on the back,but this one has nothing.does anyone have an explanation for this or has anyone ever seen this before.what would be a value on something this rare.

picture will be great help

Victor, In the mid 20th century, the higher volume "smaller" round movements that were being stripped out of unsold inventory and used in wristwatch cases very often could be made to work without a visit through the "finishing" room. So these began to "leak" profusely from the factory.