Unusually Small Machine Cancels From 1920

Is anyone able to determine what machine cancels may be reflected by the scans below?

I find them interesting because of the small diameter postmark with city and date, the fact that they were both stamped at a late hour (10 PM and 1 AM) and the fact that the machine cancel only has 6 killer bars (when most machine cancels have 7 killer bars).

I actually found two of them from close to the same period, presumably from the same post office but a different machine:

Both have the small date dial. Unversal Model DSB-300 Machine 1 & 2.