Cast, not stamped
The difference between an animal that reads as itself and one that reads as a blob is depth. A stamped charm is a flat silhouette; a cast one is modelled in the round, with the undercuts that let light find an eye or a wing. Cast pieces cost more metal and more finishing, and they are what is here.
Enamel, and how long it lasts
Hard-fired enamel is glass fused into the metal and will outlive the wearer. Cold enamel is a cured resin — brighter colors, softer surface, and it will scuff. Both are legitimate; the piece's own page says which it is.