The  article  analyses  all  documented  coin  finds  from  the fortifications in the Claustra Alpium Iuliarum defence system. The author interprets fluctuations in the intensity of monetary circulation that would reflect life or activity at  individual  forts.  Coin  finds  are  also  presented  from  archaeological  contexts  that  can  definitely  be  connected  to building activities on walled defensive structures. Data are  presented  about  the  latest  coins  from  individual  for-tifications,  which  indicate  an  interruption  in  the  regular  influx of money into circulation and thus also a break in the  intensity  of  life  at  the  fortifications.  In  this  manner,  it  is  established  that  the  first  construction  activities  in  building  the  fort  of  Castra  can  be  placed  as  early  as  the  280s, while otherwise rare coin finds in the towers of the defence system indicate building activities no earlier than the  mid  4th  century.  Coin  finds  show  an  interruption  in  monetary circulation at the Lanišče and Martinj hrib forts at  the  end  of  the  380s,  at  Tarsatica  at  the  end  of  the  4thcentury,  while  coins  also  from  the  beginning  of  the  5thcentury were found at the forts of Castra and Ad Pirum.