An iko file extension is related to the Windows Icon format. Probably obsolete format.
IKO file extension - Windows Icon resource data
What is iko file? How to open iko files?
File type specification:
The iko file extension is sometimes used instead ICO file extension for icons.
Most likely some old format without support from the developer. No further information about iko format could be found.
This iko file type entry was marked as obsolete and no longer supported file format.
This type of file is no longer actively used and is most likely obsolete. This is typically the case for system files in old operating systems, file types from long discontinued software, or previous versions of certain file types (like documents, projects etc.) that were replaced in higher versions of their original programs.