Stamps of princely state Travancore

Travancore got off to an inoffensive start in 1888, with three values on laid paper

Over the next 50 years, Travancore fleshed out this short set, adding values down to 4 Cash and up to 14 Chuckrams, on three different broad types of watermark, and in a maddening range of shades for the individual values

The occasional combination of watermark, value and (in the last years of the set) perforation is scarce, but for the most part, these are very common stamps. (The 3 Chuckrams is overprinted for official use. More, much more of that later.)

The ½ Chuckram value was surcharged in 1906:

and further surcharges followed in 1921 and 1932:

As whatever stock was on hand was surcharged, the 1932s include some scarce combinations of value, shade and watermark.
In November 1931, Travancore issued its first commemorative set, for the coronation of the Maharaja. This was only the third commemorative set from India, after the February 1931 Inauguration of New Delhi set for British India, and the March 1931 Investiture set of Jaipur. (I know which I prefer ...)

In 1937, Travancore issued another commemorative set, marking the opening of the temples in the State to castes which had previously been excluded:

In 1939, Travancore issued a long set for the Maharaja's 27th birthday; this became the definitive set for the next ten years or so:

By this time, Travancore had yet another perforator, gauging 11, and all three were used on this set, sometimes yielding compound perforations. There were also just about every form of perforation error, in various perforation gauges, you can imagine. Few of these are really outrageously expensive.
Two stamps were issued for the Maharaja's 29th birthday:

and one for his 34th, in 1946:

These all exist in various perforations and compound, and all sorts of perforation errors again. These are SG 76ba - on the expensive side for a Travancore perforation error at £40 a pair.

The last ordinary stamp Travancore issued, in 1946, was a bit of an oddity: an official stamp, overprinted SPECIAL to revalidate it for general use: