During their dynamical evolution , Galactic open clusters ( OCs ) gradually lose their stellar content mainly because of internal relaxation and tidal forces . In this context , the study of dynamically evolved OCs is necessary to properly understand such processes . We present a comprehensive Washington CT _ { 1 } photometric analysis of six sparse OCs , namely : ESO 518-3 , Ruprecht 121 , ESO 134-12 , NGC 6573 , ESO 260-7 and ESO 065-7 . We employed Markov chain Monte-Carlo simulations to robustly determine the central coordinates and the structural parameters and T _ { 1 } \times ( C - T _ { 1 } ) colour-magnitude diagrams ( CMDs ) cleaned from field contamination were used to derive the fundamental parameters . ESO 518-03 , Ruprecht 121 , ESO 134-12 and NGC 6573 resulted to be of nearly the same young age ( 8.2 \leq \textrm { log } ( t \textrm { yr } ^ { -1 } ) \leq 8.3 ) ; ESO 260-7 and ESO065-7 are of intermediate age ( 9.2 \leq \textrm { log } ( t \textrm { yr } ^ { -1 } ) \leq 9.4 ) . All studied OCs are located at similar Galactocentric distances ( R _ { G } \sim 6 - 6.9 kpc ) , considering uncertainties , except for ESO 260-7 ( R _ { G } = 8.9 kpc ) . These OCs are in a tidally filled regime and are dynamically evolved , since they are much older than their half-mass relaxation times ( t / t _ { rh } \gtrsim 30 ) and present signals of low-mass star depletion . We distinguished two groups : those dynamically evolving towards final disruptions and those in an advanced dynamical evolutionary stage . Although we do not rule out that the Milky Way potential could have made differentially faster their dynamical evolutions , we speculate here with the possibility that they have been mainly driven by initial formation conditions .