Four simple stamps
Collectors of postmark impressions sometimes forget that a completely different type of stamp was used between the so-called small circular stamps and large circular stamps. This was a trial to simplify the double cancellation that had been in effect until then, in the form of a dot stamp combined with a small circular stamp.
The commission to the Royal Mint in Utrecht was to design a larger die, but in such a way that the date and hour characters from the small circular dies could be used in the new dies. A number of test specimens were produced by the Mint's engraver. 
Two stamps were sent to the Director-General for assessment on July 12, 1893. They concerned two stamps bearing the office name 's-HERTOGENBOSCH and the date 16 JAN 1893. The dimensions of the stamp were 6 millimeters larger than the small round stamp in use. That the engraver had not fully understood the assignment is evident from the fact that he had included three other sample stamps in three different sizes and designs. 
Included with it was a stamp with the number 325. Perhaps the stamp engraver had the number or dot stamp in mind here.
Ultimately, a stamp type with a double ring was chosen, into which the date and hour characters of the small round stamp fit. Two were intended for the Amsterdam and The Hague offices for use in the Roelants hand stamping machine, and two as hand stamps for the smaller offices in Gouda and Maassluis. The four stamps were sent to the offices as test stamps on February 23, 1894. An attempt is being made to find the earliest and latest dates of use of these stamps. Will you help search? The earliest dates for the four offices so far are:
- Amsterdam: March 3, 1894
- The Hague: February 28, 1894
- Gouda: March 2, 1894
- Maassluis: March 7, 1894
- Amsterdam: January 17, 1896
- The Hague: November 10, 1895
- Gouda: February 4, 1897
- Maassluis: November 18, 1899
Good morning Cees,
If I am not mistaken, you are a (co-)author of the postmarks handbook. I have been looking for this handbook for a while.
Can you tell me where this is (still) for sale?
I would love to hear from you.
The handbook of postmarks is no longer available. However, these stamps and many other types are described on the freely accessible website of the Netherlands Academy of Philately (nedacademievoorfilatelie.nl) under the heading publications. Even the flip stamps currently in use are included here.
Thanks for your reply, Cees,
I was already afraid that it would no longer be available.
I use the site regularly. But I prefer having a catalog or handbook on my lap; I still find that more pleasant to read.
I keep searching!