Well I found the specifications for these Elgin balance staffs and I found them here of all places! Well sort of…
I know from the Swigart catalog that this watch can have one of two staffs:
An Elgin #857 long hub
An Elgin #857 short hub
Since the chart shows two sizes, I’m thinking that these short and long hub sizes are reflected in those data. According to the chart, one length is 5.97mm (0.235″) and the other 6.10mm (0.240″). My thought is because the balance staff installed in my watch measured close to the short hub (0.232″ measured versus 0.235″ specs), and my calculated length for the watch is closer to the long hub (0.245″ measured versus 0.240″ specs), that a short hub was mistakenly installed in the watch. Perhaps this would account for the excessive end shake.
Am I reaching here?