The info is at http://cache.freescale.com/files/rf_if/doc/data_sheet/MRFE6VP61K25H.pdf?pspll=1
According to curves, at 2.4 A standby current the efficiency is 62% at 700W, 72% at 1000W and 80% at 1.3 KW. Highest power with some overdriving but why not on CW.
IMD3 about -32db at 1 KW but < 40db at 700W. Probably easy to improve with minimal feedback.
The clue to efficiency is tuned and not broadband network. One MRFE6VP61K25H costs about $200 in quantity. Probably one can afford a few with different one for each frequency range.
That one is not linear, which is why it gets that efficiency.
But 'harmonics CCIR'? CCIR ceased existing 21 years ago.......
It SHOULD be to ITU-R SM329 or for Europe, ERC/REC 74-01.
Doesn't say much for a company that can't state the correct applicable standards.