Diode symbol confusion

It's supposed to look something like the letter Z -- hence, a Zener diode.

That is logical and my experience too but not in this case , hence the query. One barb represents zeners in the symbol set used on this schematic, so what does the 2 barb (normally zener) symbol mean here?

The various typefaces used by the many people who produce schematics add to the confusion and some use (often inaccurate) variations of the standard symbols making matters even worse.

There are of course yet more different types of diode, some of which also have their own symbol (and variants).

As to answer your original question, it would be hard to improve on the links JW posted.

I have seen the two barbs being each at an angle to the horizontal bar, representing a zener, and the two barbs perpendicular to the bar, representing a Schottky diode. Schottky diodes also seen as the more elaborate curl at each end of the bar, as shown in the Wiki reference.

Arfa

Shotts look more like an S for an obvious reason :)