When I saw this post I wanted to see if one of our GT’s could provide an answer and Benjamin hasn’t let me down.To put it another way. The facing is swung 5/8” at the seat line to create fullness for the chest area and the 3/8” of length added at the hem is for fullness through the button edge.
My understanding is that this is done so that when the facing is attached to the coat, it throws extra length onto the facing edge inside the coat, specifically around the chest area. This is necessary because extra vertical length has already been introduced into this region through darts and other manipulations. Hence, if you don't do this, and simply copy the existing edge of the coat when cutting the facing, the interior edge of the facing will be tight, and will not have enough length to replicate the existing shape of the coat chest area. If you want to test this, just look at what happens when you take a straight piece of cloth and move it into a curved shape - it creates ripples on the far edge.
When I saw this post I wanted to see if one of our GT’s could provide an answer and Benjamin hasn’t let me down. To put it another way. The facing is swung 5/8” at the seat line to create fullness for the chest area and the 3/8” of length added at the hem is for fullness through the button edge.
My understanding is that this is done so that when the facing is attached to the coat, it throws extra length onto the facing edge inside the coat, specifically around the chest area. This is necessary because extra vertical length has already been introduced into this region through darts and other manipulations. Hence, if you don't do this, and simply copy the existing edge of the coat when cutting the facing, the interior edge of the facing will be tight, and will not have enough length to replicate the existing shape of the coat chest area. If you want to test this, just look at what happens when you take a straight piece of cloth and move it into a curved shape - it creates ripples on the far edge.