In a sense, of course, 'he' refers to the creator mentioned throughout the poem. However, 'he' may also refer to Blake himself, who in a very real sense did indeed make both "The Tyger" and "The Lamb" of Experience and of Innocence.
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indeed, the identical impression sizes of the two plates suggest very strongly that "The Tyger" was etched on the opposite side of the copper plate which had "The Lamb"...