Typical anti-metal stickers have a sticky ferrite layer that is expected to be placed or stuck on metal surfaces and the other side will be tapped on by the mobile or reading device. REVERSE anti-metal NFC stickers would normally be placed inside cases where the antenna is place against a plastic surface and the anti-metal protection is provided against metal or electrical circuits in side. Other uses might be where you have a pister in a metal case and you would place the sticky side on the back of the poster where the tag will get tapped, but the back is against the metal casing ans is protected.

They are basially the same, but the layers are structured differently. Pease see the pictures of the layers.