"It is just an illusion, manufactured in a lab next to the sarcophagus..." The subject matter of this article was cut from the final version of a S.T.A.L.K.E.R. game.
The Duty SPSA-AUT self-cocking shotgun is made only in Duty workshops. This weapon is intended for fighting large groups of mutants. Its improved feeding mechanism ensures a high rate of fire, and the magazine capacity has been increased to 10 rounds. Uses 12x70 caliber rounds. - Call of Pripyat in-game description
A special variant of the SPSA-14 shotgun created by the Duty faction, it would have been made specifically for mutant hunting. It would have an improved fire rate and would hold 10 rounds instead of 8. The variant would also make the use of Slug rounds impossible.
The variant cannot be spawned due to the lack of configs file in the w_spas12.ltx file. The only proof of its existence are the strings st_wpn_spas12_m2 and st_wpn_spas12_m2_descr in the st_items_weapons.xml file. Strings for the weapon are found in the files of both Clear Sky and Call of Pripyat.
It is worth noting that in Call of Pripyat there is a special variant of the SPSA-14 named Carabiner that has both an improved fire rate and mag capacity, among others. It can be assumed the SPSA-AUT served as a placeholder for the Carabiner before it was finally replaced.