Slaughterhouse Soviet tech skins are available on Elite or Nightmare mode, depending on the weapon. They can also be purchased as a Weapon Mould in the item store. Outfit worn is the Red Hand Winter Uniform from the Master Planner achievement.
The rare skins available only on Nightmare mode are: Re-Purposed Scythe blade, Mara’s Book of Names blood focus and Tsar Gun shotgun.
Nightmare mode Slaughterhouse also drops Kyshtym Revolver which shares a skin with the Walther PPKs from The Facility Elite, and the Fangs fist weapon which have the same skin as Meteor Shard from The Facility Elite.
Thank you Shaun2406 for the screenshots.