Lewis & Short

archĕtypus, a, um, adj., = ἀρχέτυπος, that was first made, original (very rare): archetypos servare Cleanthas, i. e. the original statues of Cleanthes, Juv. 2, 7. So Martial calls the original MSS. of his epigrams, archetypae nugae, 7, 11, and in jest, friends that cost nothing, archetypi amici, 12, 69.
Hence, subst.: archĕty-pum, i, n., an original, Varr. R. R. 3, 5, 8; so Plin. Ep. 5, 10; Macr. S. 7, 14.