TPO -> The TPOs (Ambulancias) of Chile
The TPOs (Ambulancias) of Chile
By Alan Codling
The first railway in Chile opened in 1851, and the first TPO was introduced in 1862. However for the first thirty years of operation of the system no postal markings have been found that can be attributed with certainty to TPOs. This may be because the clerks were using dumb cork or pen cancels (as were many other postal agencies in Chile at the time), or that the mail was taken to the nearest fixed Post Office for cancelling.

1892 Ambulancia cancellation
In 1892 the Head Post Office in Santiago started marking mail (probably only the top item in a bundle) on the reverse with "Ambulancia" in an oval frame, to indicate that it was to travel by TPO. The first "on train" Ambulancia datestamps were issued on the 20 January 1894 and were single ring with route termini. Special postage due (Multada) handstamps were also introduced on certain routes.

Single ring AMBcia TPO cancellations indicating route termini

Multada TPO cancellation indicating 2 cts postage due
However the datestamps were made of brass and rapidly wore, so much so that they became almost illegible. From 1896 new handstamps were larger and double ring, although they still included the route termini. These were in use until 1911, when a major revision of the system took place and 85 numbered datestamps came into use.

Double ring AMBcia TPO cancellation indicating route termini
Initially the numbers of the routes ran from the north to the south of the country. They are a challenge to study, as although some remained on the same line for 50 years or more, many were moved, in some cases several times. Several lists of route allocations have been found and published, but these are only snapshots of the situation at a particular time, and it is often difficult to determine on which route an Ambulancia was running. As new lines were built new numbers came into use and eventually the sequence reached 150. A small number of datestamps were issued in the 1920s with both a number and route termini (see Ambulancia 95 on the cover below). The last Ambulancia ran in June 1988.

TPO cancellation indicating route number (44) and route number (95) and termini
References
Alan's 16 page exhibit shown in Santiago in November 2010 is posted here.
An excellent guide to this subject is "The Travelling Post Offices of Chile" by Sr. Emmerich Vamos Sz., published by the Mobile Post Office Society in 1983. It is out of print but still obtainable on the second-hand market.
New Book on TPOs of Chile
This new book by Alan Codling is now available, click for the flier: The Travelling Post Offices (Ambulancias) of Chile. This work complements rather than replaces Sr. Vamos's book.