[Coco] trouble with AR

[Aaron Wolfe]

I've had lots of trouble unpacking the .ar files found on RTSI.  I
have ar v1.3 and ar v2.0.

For instance, the file ftp://www.rtsi.com/OS9/OS9_6X09/UTILITIES/uptime.ar

with ar 1.3:

{N2|03}/DD/TMP:ar -x uptime.ar
extracting <uptime>
ar: file not archive or damaged
ERROR #001

with ar 2.0:

{N2|03}/DD/TMP:ar2 -x uptime.ar
extracting <uptime>
ar2: file damaged - no header at $12FE
ERROR #001

Anybody know exactly what version of 'ar' I should be using?
Sometimes a .ar file will work for me, but a lot of them don't.
I have a feeling I figured this out once, but I'm not doing so well
this time around.
-Aaron