The dated precancels shown in some of the above images include "SRC" (Sears, Roebuck and Company) and "MW" (Montgomery Ward), two of the most prolific users of precancels and therefore value is negligible.
More on that specific precancel collecting discipline excerpted from one of many websites on the subject:
Quote:
Starting in 1938, the user's initials plus the month of use was required to be printed on denominations over 6 cents. The value of printed dateds is usually less than a nondated precancel. The value of printed MW (Montgomery Ward) and SRC (Sears Roebuck) are more common than other printed dateds. Handstamp dates are worth less than printed dateds, and MW and SRC handstamp dateds are the most common...There are exceptions for stamps from low piece-count mailings and rare months of use. The Official Printed Dated Control Precancel Catalog, 6th Edition (2001) is the current reference.