"4 fortes pièces inox" - equates roughly to 4 strong steel pieces, so as noth suggest - I would think he means tools in that context.
" très bon état, toutes pièces propres sans marque notable d'usage - coupe extra - pas de jeu, ressorts souples et puissants"
= Very good state (
condition), all pieces show no noticeable marks from use - extra cut(
) - no play, springs flexible and powerful (
so - good snap).
That's pretty close I think.