Change the voice: We have gifted him a watch.

A watch was gifted to him by us.

A watch had been gifted to him by us.

A watch has been gifted to him by us.

None of these

Active voice: We have gifted him a watch.

Tense: Present perfect

Object to become subject: A watch

"have gifted" changes to "has been gifted" (singular subject)

So,

Passive voice: A watch has been gifted to him by us.