There is only one file type that uses the .TCN extension:
Techne Model File
Model created by Techne, a Windows program used to design models used in Minecraft; contains data that describes the model, which includes dimensions, position, and texture; can be edited in Techne.
NOTE: In the Techne program, TCN files can be exported to the "Texturemap", "Turbo Model Thingy", "AdventureCraft", and "Java" formats.
Updated: March 26, 2019