I own an older Heuer watch, probably 25-30 or so years old, before TAG joined ... it's a diver's watch .. the face is black, day box only on the right side at 3 o'clock, black moveable dial with gold edge, metal band, wording on the face "Quartz 20ATM Professional' ... the hour hand has what looks like a Mercedes three-pointed star elblem ... on the back,the words Etanche, Acier .. also, 20 ATM and the numbers 980.020 and 27958 ... just got it back from Tag Heuer authorized repair shop, all it needed was a new battery .. it's in excellent condition and keeps perfect time; any idea how much it might be worth? thanks!