In 1892, after the incorporation of several suburbs into Bezirke 11-19, all Vienna's Post Offices were renumbered, and new types of cancellers introduced. This was issued as Circular-Verordnung Nr 28 dated 12 December 1891 by the Post- and Telegraph Direktion. One of its many paragraphs said: "If the individual k.k. Offices already have the aforementioned new cancellers and seals, they are immediately to put the same into service; if not then this shall be done when they arrive."
The 1892 cancel format was 'WIEN' at the top followed by the delivery district; in the middle the time and date with month in roman numerals; and at the bottom the office number (or letter) between ornaments, usually followed by 'r' for Rohrpost.
When did the renumbering start? Post & Telegraph Ordinance No28 was issued 12 Dec 1891, but is silent as to when the renumbering came into effect. It appears to have been Jan 1 1892. This card shows that although Telegrafen-Centrale was still using the old instradierungschiffre (Station No 10 - renumbered 40) at 1:00 pm Dec 31, 1891, Landstrasse had one of the new money-letter cancellers on-hand and used that!

Use of the Landstrasse money-letter cancel 'g 40' on pneumatic mail on 31 Dec 1891./
Verordnung Nr 28 instructed offices that had not yet received the new cancellers to use them as soon as they arrived. When did 40 & 57 get the new pneumatic mail cancels? The earliest use found for pneumatic cancel 40 is 23 Jan 1893 (sample of 11) but for 57 is 12 September 1893 (sample of 3).

Use of 'g 40' cancel at Landstrasse & regular post cancel at 57 (Gumpendorf).
Stations may have used new 'regular post' cancels to obtain correct station number wwhile awaiting delivery of Rohrpost cancels. Use of 'g 40' cancel at the Landstrasse Rohrpost counter was persistent! May, 1992 usage: six examples have been discovered.

Still being coded to '10' when it should be '40'.