BK2 file extension is for Timed backup file for document window 2
WordPerfect for Win
Similar to BK2
A11 - AIM Graphics file
A21 - Soundweb Firmware File
A2A - APLASCII EISPACK file
A2A - IBM Voice Type Language Vocabels File
A2A - Sharp APL Workspace Export File
A2B - A2B Player Playlist
A2M - AudioToMidi Settings file
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