This article or section refers to legacy content that was inherited from previous game and/or engine releases and were not meant for use in the current game and/or engine but may show up in the in-game files.
The MP5 SD also know as Heckler & Koch MP5 SD was a placeholder weapon used during the development of Ritual Entertainment's build of Counter-Strike: Condition Zero (Deleted Scenes).[1]
The only trace left of it is an unused model located in the Deleted Scenes' files. "urban.mdl" which is a model for an Arctic Avenger using Half-Life's HECU animations, most of which were probably placeholders.