So, the three points of comparison are
1. The opening
2. The edge at the top of the hook
3. The presence or absence of a pin limiting travel of the hookAttachment 47515Attachment 47516Attachment 47517
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The above concerns standard rifle length scabbards. Cadet length scabbards are another story with at least five variations.
Thank You - Great explanation and photos - now I know what to look for.