Hi dtrudel
It means the following:
AWS = American Welding Society
A5.20 = The specification for carbon steel electrodes for FCAW
E = Electrode
71 = 70 ksi tensile strength and all position weldability
T = Tubular electrode
-1 = Usability designator
M = Classified with 75-80% argon, balance CO2.
-9 = Essentially the same as -1, but with improved impact properties.
In short, it does mean that they are duel certified:
AWS A5.20 E71T-1M AND AWS A5.20 E71T-9M
In this combination it does however mean only a very small difference in the specification requirement. -1 has an impact requirement of 20 ft lbf at 0°F, while -9 has an impact requirement of 20 ft lbf at -20°F
Hope this answers your question.
Regards
Niekie Jooste
Fabristruct Solutions