Be glad you've never had my experience. I got stopped by a keystone cop (except this one wasn't so lazy) in front of the US consulate in Osaka earlier this year. He asked for my gaijin card, which I promptly showed him. Turned out he didn't believe the visa extension stuff on the back and such (which had the ward office hanko and the tape over it), so he asked me to go to the koban to "investigate" it. What happened was a 20 minute diversion which ended with him on speaker phone to the main police station, which was telling him that yes, if it has a hanko and tape over it it's ok, don't worry (and him being unsure of this). He then walked me to my bike (right across the street), where he wanted to see the registration, which I promptly didn't hear him ask for until after he had carried the bike across a bridge. I went to the police station the next day to complain about this guy's not knowing proper rules (as complaining about asking for the card probably would have resulted in the exact same thing, a day later) and asking them to ensure their officers knew everything.