Tokyo (CNN) A new device aimed at tackling sexual harassment on crowded trains and public transport has sold out just half an hour after it went on sale in Japan.

The "anti-groping" stamps, manufactured by stamp-maker Shachihata Inc., allow victims of harassment to mark their assailants with invisible ink , and also provide a deterrent to would-be attackers.

A limited run of 500 stamps, which retailed at 2,500 yen (about $24), sold out within 30 minutes of going on sale on Tuesday, a company spokesman told CNN.

The stamp marks an assailant with a palm shape in invisible ink.

In May, Shachihata said it would develop the stamp after discussions erupted on social networking sites about how to discourage groping -- known as "chikan" -- on crowded trains.

One social media user suggested pricking the offender's hands with a safety pin, while others pointed out that this could be a crime in itself.

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