Sofia's trams, such as this,no 703, carried post office letter boxes beside the entrance. These were in use, as evidenced by a test letter which made its way back to Surrey in a week or two. This 1984 car is a Sofia T6M 700 of which 60 entered service in the perioe 1984-7 according to this excellent web site. The site also has a route map, inter alia, for 1994.