Importing a historical car (oldtimer) into Turkey (Istanbul)

As (like always with my bad turkish language knowledge ...) its impossible for me to find some reliable information in the web or the original text of the turkish law i would be happy if someone could help me out:

we organized an historical russian car (build in Protected content an exhibit for our customers exhibition booth (car registered in russia, was driven to turkey on his own wheels and registered into the drivers passport, so far so good...). now my customer wants to buy the car as he has fallen in love. i heard one time that there is a special regulation (more easy) to import classic cars into the country but i could not find anything about it. does anyone know or has made his own experience ?

as the customer is a turkish citizen the blue plate regulation is no option here, i need to get an official turkish ruhsat.

thanks
alex