This is a sub-page of Splatoon 2/Unused & Unobtainable Gear.
SLO017#

Added as the Suede Gray Lace-Ups in 3.0.0, but they're less detailed versions of the Suede Nation Lace-Ups in 2.0.0. The gear entry is work-in-progress, and the brand is set to Zink.
SHI010#

Added as the Chocolate Dakroniks in 3.0.0, but in 1.0.0 they were colored yellow and blue, and have a placeholder gear entry.
SHI021#
Added as the Milky Enperrials in 2.1.0, but in 1.0.0 the model is untextured. The gear entry appears complete, and the ability is Special Saver.
SHI022#

Added as the Navy Enperrials in 2.0.0, but in 1.2.0 they're Milky Enperrials with a blue sub-color instead of red. The gear entry appears complete, aside from a placeholder price, and is set to have the Run Speed Up ability.
SHI024#

Added as the Yellow Iromaki 750s in 2.0.0, but in 1.2.0 they were Black Norimaki 750s with pink-to-sky blue soles. The gear entry appears complete, aside from a placeholder price, and is set to have the Bomb Defense Up ability.
SHI025#

Added as the Red & White Squidkid V in 3.0.0, but they have an earlier design in 2.0.0, with a work-in-progress gear entry. The brand is set to Tentatek.
SHI026#

Added as the Honey & Orange Squidkid V in 3.0.0, but they have a different design in 2.0.0, with a work-in-progress gear entry. The brand is set to Tentatek.
SHI034#

Added as the Red Power Stripes in 3.0.0, but they have an earlier design in 2.0.0, with a darker green and no spots on the soles. The gear entry is work-in-progress, and the brand is set to Tentatek.
SHT010#

Added as the Violet Trainers in 2.0.0, but in 1.0.0 they were colored orange, and have a placeholder gear entry.
LTS011#

Added as the Annaki Tigers in 3.0.0, but in 2.1.0 they were a light brown-colored version of the Annaki Habaneros. The gear entry is work-in-progress, with the ability set to Sub Power Up.
MSN105#

Added as the Null Boots Replica in 3.1.0, but they were a pair of yellow rollerskates in 3.0.0, and have a work-in-progress gear entry. Rollerskate-based Gear would appear in Splatoon 3 as the Trevally Derby Rollers.
RVL001#
Early versions of the rival Neo Octoling Boots can be found in 1.0.0. The male model is a work-in-progress, lacking the belts and using basic textures.
The other early version can be found within the unisex model, but only textures remain. The text "NEW" can be found in the albedo texture.
COP104#
Added as the Friendship Bracelet in 4.8.0, but it was a generic leather bracelet in 3.0.0. The gear entry appears to be complete.
COP105#
Added as the Flipper Floppers in 4.0.0, but they have an earlier design in 3.1.0, with no detailing done on the model. The gear entry appears to be complete.
Another early version can be found within the unisex model, and the only difference from the final seems to be the rotation of the shoes.