END cels / "A1 END" cels / Tome (止) Cels
An END cel (marked with either END/ E/ or the kanji 止) is the last cel in an animation sequence. A1END cel setups are sometimes referred to as Tome/止 cels. When a cel is marked with a letter A/B/C/E..+ 1 + END/E/止 then that means it is the only cel for that particular animation sequence. So an A1END cel setup starts and ends with only that frame. Since there is only a single frame in this type of setup it will generally bring up the value of a cel/setup depending on the quality of the image. In the case of a multiple cel setup, a B1End/止 will increase the value of the setup, because any other setups with the A2 or C3 for example will always be missing that B1End/E.
Below are examples of how an A1 end cel can be labeled
1st is "END"
2nd is "E" with a circle around it
3rd has the kanji "止"