postage franking vs franking

postage franking and franking both are nouns.

Word	Noun	Adjective	Verb	Adverb
postage franking	Yes	No	No	No
franking	Yes	No	No	No

As nouns, franking is a hypernym of postage franking; that is, franking is a word with a broader meaning than postage franking:

postage franking: postage stamps, or any other markings recognized and accepted by the postal system or systems providing service, which indicate the payment of sufficient fees for the class of service which the item of mail is to be or had been afforded.
franking: device or marking such as postage stamp, printed or stamped impressions, codings, labels, manuscript writings, or any other authorized form of markings affixed or applied to mails to qualify them to be postally serviced.

Other hypernyms of postage franking include frank.

postage franking (noun)	franking (noun)
postage stamps, or any other markings recognized and accepted by the postal system or systems providing service, which indicate the payment of sufficient fees for the class of service which the item of mail is to be or had been afforded.	device or marking such as postage stamp, printed or stamped impressions, codings, labels, manuscript writings, or any other authorized form of markings affixed or applied to mails to qualify them to be postally serviced.