An other thing to not get too concerned about is finding a pen has lost its code. The first date codes, found for example on the Vacumatics, consists of two digits, the first one denoting the quarter of production, the second denoting the production year.
In addition, I have been able to inspect a demonstrator with the "1" imprint by the clutch ring and a rounded blindcap.
Some collectors speculate that the ones without a datecode are really pre-production models from 1940.
Another explanation may be that they were never dated or that the datecode wore off (on most instances the datecode is lightly imprinted to begin with).
In the second quarter of 1938 this system was however changed to save production time, and a new date code, using a system of dots, was adopted.
The stamp initially had three dots and for each quarter one dot was filed down leaving none for the fourth quarter.