The first open edition NFT (afaik) was created by Pak. The 28 August 2020 collection "X by Pak" on Nifty Gateway included 13 "infinite editions," the first instance of what would later come to be known as "open editions."
The concept was phrased as follows: "X's 'infinite editions' (x/n) are not limited with count, but limited with time. One single day of infinite existence. In other words, the less each 'moment' in X is collected, the less copies it will have. A dynamic balance of value defined by demand, reversed. X starts with The Touch and ends with The Void."
And earlier example of a proto open edition is PEPECASH, an edition of 693,187,961 released on the Bitcoin blockchain in Season One of the Rare Pepes collection in September 2016. This edition was an airdrop to all Rare Pepe collectors, but its scale and its intention form the groundwork for what would become open editions.
Perhaps the best-known open edition is Max Pain by XCOPY. I hear it will be revealing soon.
Decagons. Decagons by Deca x Kjetil Golid, Deca's membership token, are a truly infinite edition, open to all for all time.
Lift. Lift is perhaps the most innovative and meaningful form of open edition currently in existence. Lifts are a feature of the Etch tool created by Deca in collaboration with Matt Kane. One can "lift" an Etch, which distributes a selected amount of ETH to the holder of the respective Etch. Every Etch can generate a potentially infinite open edition of Lifts. To inaugurate Lift, Deca had a fundraiser to support four non-profit organizations. These Etches can still be lifted, and all proceeds will be automatically transferred to the lifted organization.
A HISTORY OF CRYPTOART is an epic painting by SuperRare OG Panter Xhita depicting 90 founding figures of the CryptoArt scene . It was released as a set of 3 open editions which could be burned and combined to create the full triptych. The subjects depicted are (in no particular order): Matt Kane / Xcopy / Josie / Coldie / Carlos Marcial / Alotta Money / Fewocious / Eclectic Method / Osinachi / Bea and Judy from Dada / Hackatao / Moxarra / Neurocolor / Kitty Bast / Beeple / Stina Jones / Robness / Artnome / Yosnier / Fabio Giampietro / Ann Ahoy / Frenetik Void / Raf Grassetti / Micah Johnson / WGMeets / Pranksy / Jose Delbo / Olive Allen / Katy Arrington / Pak / Skygolpe / Rutger van der Tas / GusGrillasca / Bryan Brinkman / Xelda Jara / 3LAU / Trevor Jones / Mattia Cuttini / Gisel Florez / Travis LeRoy Southworth / Sarah Zucker / Lucho Poletti / Jivinci / Refik Anadol / Sparrow / Billelis / Lethabo / Rare Pepe / Mad Dog Jones / Videodrome / Angie Taylor / Fvckrender / Victor Mosquera / Pindar Van Arman / Miss Al Simpson / Stellabelle / Norman Harman / Hex6c / Kristy Glas / Fabiano Speziari / Martin Lukas Ostachowski / Slimesunday / Oficinastk / Giant Swan / MightyMoose / Max Osiris / Lapin Mignon / Shortcut / Kevin Abosch / Joy / Gary Cartlidge / Leozeba / Pascal Boyart / Bard Ionson / Rare Scrilla / Daniella Attfield / HairofMedusa / Yusaymon / Rhea Myers / Mbsjq / Killer Acid / Danil Pan / George Boya / Snowfro / Tyler Hobbs / Ekaitza / Dmitri Cherniak / Han / Parrott / Yura Miron / Manolo Gamboa Naon.