Too many small, good brands to list. The usual sign of a decent quality frame that can show no matter how bad the wear on labels and paintwork is the use of investment cast rear dropouts. These have a moulded shape in contrast to the stamped sheet-metal dropouts of cheaper bikes.
With lugged bikes, cheaper ones have a large step in thickness between lug and tube, better quality ones use thinner lugs or have a graduated reduction in thickness from filling the lug.