Those are glass passivated diodes if that helps at all, doesn't mean they're a Zener, many small signal diodes are glass passivated. Zeners are almost universally low voltage so hook it up to a 20-40 volts supply in reverse with a limit resistor to keep it from blowing up and measure the voltage drop, if there is one that will be the Zener voltage, if it smokes it's not avalanche rated =)
I'd lean towards cobra's suggestion that they're just common 1/4-1/8th watt small signal diodes, good for lots of things.