The Collaborative International Dictionary of English v.0.48:

Horologer \Ho*rol"o*ger\, n.
   A maker or vender of clocks and watches; one skilled in
   horology.
   [1913 Webster]

WordNet (r) 3.0 (2006):

horologer
    n 1: someone who makes or repairs watches [syn: watchmaker,
         horologist, horologer]