Hanken Cel (版権セル) / Hanken sketch (版権原動画)
Hanken cels are super rare one of kind cels made for use in for in promotional items like magazines, cards, merchandise, posters, calendars, etc. They are usually made by an animation director, character designer, or senior animator. Hanken cels are usually hand inked and hand-painted. Because hankens are generally very recognizable, high quality, and one of kind they are usually very pricey and can be very hard to get as most studios do not sell them to art dealers for sale. In some cases studios produced copy Hankens in numbered editions of around 100 specifically for collectors to buy.
Hanken drawings also come up for sale. The rough (genga) and finished ( douga) sketches used to make the final Hanken cels are generally a bit easily to find and more affordable.
Sailor Moon Hanken (image taken from Mandarake Auctions)
Sailor Mars / Rei Hanken (image taken from Mandarake Auctions)
Card Captor Sakura Hanken Douga (image taken from Mandarake Auctions)
Card Captor Sakura Hanken Douga Copy with Shadow Designation (image taken from Mandarake Auctions)