Mike said:

>Most infrared and superbright LEDs are exactly the opposite.  Looking at
>the internal parts is not a good way to tell.  The standard marking
>method is based on making the lower flange of the LED's plastic shell not
>quite round.  There is a flat spot next to the cathode lead.  Also the
>cathode lead is shorter than the anode lead, of course that works only
>for new LEDs.
>

  The convention of identifying T1 and T1 3/4 LED cathodes with a
  flat is the closest thing to universal that I've ever seen. Has
  anyone ever seen an exception?

  Reg Neale