The most common AFM file is a small text file giving information about a font. You can check for this in two ways
1. The files will be pretty small (mostly 25KB or smaller)
2. The files can be opened in NotePad where there will be lots of readable (if nonsense) text like
StartFontMetrics 2.0
Comment Copyright (c) 1984 Adobe Systems Incorporated. All Rights Reserved.
Comment Creation Date:Sun Feb 8 18:48:01 PST 1987
FontName Helvetica
...
StartCharMetrics 228
C 32 ; WX 278 ; N space ; B 0 0 0 0 ;
C 33 ; WX 278 ; N exclam ; B 124 0 208 729 ;
C 34 ; WX 355 ; N quotedbl ; B 52 ...