AC as Armour simply means the Armour Class of the creature being described is equal to whatever armour that individual is wearing - likewise for Damage as Weapon.
This was originally written for use with Original Dungeons & Dragons (OD&D), using the retroclone Delving Deeper which is a cleanup and restatement of the original text. You can find digital copies of Delving Deeper online for free. Notably, OD&D and many of its derivatives use a d6 for all HD and most damage - any increase beyond a flat d6 represents a monster able to deal damage beyond the limits of a human.
Additionally, my own work, Wolves Upon the Coast, uses this as the only monster manual.
Hope this helps!