I was off elsewhere on my lawful occasions while all this was going on, but I see that naughty Young Rodney has misled you Gord.
The first stamp isn't actually from Travancore, but Travancore-Cochin. After India gained independence in 1947, the former princely states were absorbed into the new India. As part of this process, Travancore was merged with the neighbouring State of Cochin on the 1 July 1949, to form the United State of Travancore-Cochin, which changed its name on the 26 January 1950 to Travancore-Cochin.
Under the merger terms, Travancore gave up using its old currency of chuckrams (you'll see the first stamp is denominated 4 Chuckrams) and adopted Indian currency, which Cochin State had been using for some years. Four Chuckrams was just about equivalent to 2 Annas, so the Travancore stamp was surcharged 2 Annas in Indian currency. Here is a cover from Travancore-Cochin, with a Cochin 3 Anna and a surcharged Travancore 4 Chuckram/2 Anna stamp like yours, making up the registered letter rate:

(I suppose naughty Young Rodney choked at having to concede that Travancore had been joined to Cochin, and couldn't bring himself to write the dreaded word 'Cochin'.)
It would be well worth checking the perforations on your third, purely Travancore, stamp. Gibbons lists this stamp perf
12½ at £14 used, and if it's a mixture of perf 12 and 12½, at £32. Perf 12 on all four sides, it's only a 10p job, I'm afraid.