Final answer:
Seam allowances of at least one-half inch are a clear indicator of high-quality construction in a ready-made garment, as they allow for secure seams and potential alterations.
Step-by-step explanation:
When assessing the quality construction of a ready-made garment, several characteristics can be indicative of high quality. However, among the options provided, seam allowances of at least one-half inch tend to be a good indicator of high-quality construction. This allows for enough fabric to ensure that the seams are secure and can be altered if necessary, contributing to the garment's longevity. Stiff interfacing, darts with 'dimples' at the points, the use of monofilament nylon thread, and large buttonholes do not necessarily signify high quality and, in some cases, might suggest lower quality workmanship.