When purchasing stock wool, the primary focus should be on storage conditions and fiber integrity. You must verify the wool content percentage (e.g., 100% wool, 70/30 blend) through a burn test or lab report. Check for signs of aging such as moth damage, 'shelf-smell,' or color fading along the creases. High-quality stock should maintain a soft hand-feel and natural elasticity; if the fabric feels brittle, it may have been stored in a low-humidity environment for too long, compromising its durability.