The group had developed a complicated but very effective system of disguising stolen cars, known as the 'doubles method'. Later, the officers of the Federal Criminal Investigation Office reacted to it with surprise and professional appreciation.

It involved members of the group stationing themselves in car parks outside apartment blocks. As soon as a car of the desired type turned up, they followed the driver to his apartment. A few days later they rang his bell, equipped with identification from an opinon poll outfit, and asked for details of his vehicle. After that a new logbook was forged, containing all the relevant details: owner's name, date of first registration, licence number, make, colour. Then they went in search of another car which exactly fitted the same technical data. They stole this duplicate and gave it number plates identical with those of the first car they had picked out. Thus there were suddenly two cars of identical appearance and with identical number plates around. If the police stopped someone in one of these 'doubles' and checked up on him, inquiries put to the Federal Motor Licensing Bureau would elicit the information that such a car really was registered in the name of such and such a holder and had not been reported stolen.