For the first several years of collecting serial numbers, there was not too much excitement to be found in the 845 grade, in fact it was kind of boring.  It was only made in one jewel count, that being 21.  Aside from the movement variations that occur in all grades and the plugged balance cock, there was nothing of interest and no mysteries to be unraveled.  Suddenly it was found that Waltham had not let us down.  The first run of 845s listed in the Gray Book is 12,577,501-12577600, a run of hunting case movements.  The first run of open face movements listed is 12652001-12652200.  What  made the situation intriguing was the appearance of 845 movements with serial numbers previous to the above listed runs and the intrigue is tied mainly to the Appleton Tracy & Co. grade.  The Gray Book lists 2 runs of the Appleton Tracy & Co. (ATC) grade as being 17-21 jewels (12002001-12002300) and (12577601-12578000).  To date there have been no ATCs reported as having 21 jewels but there have been three 845 movements reported from the 12577601-12578000 run along with four ATCs.  Table EIG1 shows that other 845s have been reported from ATC runs and three Crescent Street run previous to the 12577501 run.  The table also shows a later run, 16079701-16081000 which the Gray Book indicates as being Crescent Street/845.   Aside from private label movements, there is only one area that would be considered an anomaly in 845 production.  Movements from the 14125301-14125400 run have 08 regulators with solid balance cocks and the groove on the outer edge of the movement, next to the balance wheel.  The 08 regulator with the solid balance cock first appears 16125201 and the groove begins to appear intermittently around the same time and then consistently at 17077001.  It would appear that this run is some sort of retro-fit.  Production of the 845 grade rockets past the combined production of 21 Jewel Vanguard and Crescent Sts after the 12 millions.  A table displaying production figures for these movements can be seen here.