Smartcards having (i) a metal card body (MCB) with a slit (S) overlapping a module antenna (MA) of a chip module (TCM) or (ii) multiple metal layers (M1, M2, M3) each having a slit (S1, S2, S3) offset from or oriented differently than each other. A front metal layer may be continuous (no slit), and may be shielded from underlying metal layers by a shielding layer (SL). Metal backing inserts (MBI) reinforcing the slit(s) may also have a slit (S2) overlapping the module antenna. Diamond like carbon coating filling the slit. Key fobs similarly fabricated. Smart cards with metal card bodies (MCB). Plastic-Metal-Plastic smartcards and methods of manufacture are disclosed. Such cards may be contactless only, contact only, or may be dual-interface (contact and contactless) cards.