When sourcing from a watch factory, you must prioritize the movement type, as it determines the watch's longevity and accuracy. Look for factories offering Japanese Miyota or NH series movements for reliability, or Swiss-grade ETA clones for high-end performance. Additionally, ensure the casing uses 316L or 904L stainless steel for corrosion resistance, and the crystal is made of scratch-resistant sapphire glass with an anti-reflective (AR) coating. For dive-style watches, verify a water resistance rating of at least 5ATM to 10ATM through vacuum pressure testing.