4 minutes a day is not bad for a replica.
I had a genuine omega speedmaster and it lost about 10 minutes a day.
Most replicas have no q.c. and I don't think my genuine omega has cosc q.c. either.
My newly arrived 127 with swan neck is definitely not sapphire as it has a big scratch on the crystal and a hair or lint inside the crystal. It has all the correct bridge, and swan neck, 117 serial, but is not ar coated. I bought the piece from a respected dealer on the forum. I am still waiting for answer from him, hope the issue will be resolved soon.
I have a non AR 117 . It has a big scratch on the crystal. Is 117 with sappihre or mineral? Sapphire is not supposed to get scratched that easily. My friend received the Eddie's 581 version and it definitely has the AR but with more distortion on the len especially than my 117.