I have a client that is a major aerospace player that uses a paint striping system to identify their GTAW filler metals. Essentially, their system uses four different colored paint bands around one end of the filler metal. The end with the paint bands is the stub end to prevent contaminating the weld puddle.
This system requires a chart with the colors to decypher the color code, but the major advantage is that there are no little flags to fall off. Trust me, they will fall off.
Most specification require a system for maintaining the filler metal classification, be it impression stamping, etching, flag tags, or paint striping. The method isn't usually as important as it is to maintain the integrity of the filler metal identification. The bands of colored paint is about as positive a means as there is when the wire is too small to impression stamp.
Best regards - Al