Can the 4 mm caliber 'EKOL' revolver (Flaubert) be considered a firearm?

I read the news that a man threatened a saleswoman with a revolver and took cash from the cash register. The court sentenced him to 5.5 years in prison. But I don't understand whether the court correctly classified the 4 mm caliber "EKOL" revolver (Flaubert) as a non-firearm? Did this affect the sentence?