Chas. Cole & Co., Geelong. 13oz Amethyst Torpedo bottle.

Sun coloured torpedos are extremely unusual.
Amethyst glass like this is produced when manganese oxide in the glass mix is exposed to sunlight. Originally the manganese was added to neutralise the effect of Iron impurities in the sand used for most glass, this made the finished article clear rather than the usual green-aqua. However the amount of manganese oxide is critical and when too much was added the Ultraviolet radiation from the sun would slowly ionise the compound turning the glass purple.

Chas. Cole used a huge range of bottles and all are highly collectable because of the attractive "sea eagle grasping a fish" trade mark