Following a heated online debate on ways to combat groping and similar behaviors on trains, a name stamp-maker on Tuesday released a new product that can be applied to the offender's hand — leaving the seal mark of an open palm to identify an assailant.

Developer Shachihata Inc., which makes easy-to-use pre-inked seals, hopes the product, priced at ¥2,500 before tax, will help deter the common problem on Japan's crowded trains.

A limited trial run of 500 sets sold out in less than an hour after sales began at 1 p.m. Tuesday, company spokesman Hirofumi Mukai said.