Here are two different Estonian Narva to Tapa rail route t.p.o. (postvagun 8) cancels. As with many European t.p.o.cancels, they are too large to fit on one stamp. These are mostly complete on the pairs. The first cancel is 35mm x 24mm, and the second one is 33mm x 25mm (Estonia Philately Handbook
Hurt and Ojaste). Usage of these cancels began in 1927.
And, here is a another Estonian t.p.o. which is slightly older (1920 beginning usage). This is from the Valk to Tallinn route. It is also shown superimposed over its illustration in the Hurt and Ojaste handbook to show how the complete postmark would appear.