The Acronym AMF refers to the machine that creates the stitch, manufactured by the company American Machine and Foundry. This machine is extremely slow and using AMF takes a very long time.
AMF Stitching is a sign of a quality made-to-measure or bespoke tailored suit.
The stitch keeps the jacket's interlining in place with regard to the outer fabric. Another benefit of this type of stitching is that it keeps the edges flat and clean and prevents them from rolling or curling.
The AMF Stitching can be two millimeter or six millimeter away from the edges of the jacket.
The color of the AMF stitching can be the same as the jacket fabric for a formal look and can be in contrast color for a more casual or statement jacket.