Sys Info will do it. Plus I "think" if the power LED is green/yellow instead of red then it tends to be an ECS model. Motherboard revision 6.3 onwards is ECS I believe.
just checked the BBAH and they confirm it.
I am pretty sure that 6.2 has the 1 meg Fatter Agnus, but the OCS Denise. However it is very easy to upgrade to an ECS Denise. Anyway, like stated earlier any program like AIBB, or Sysinfo, or Showconfig will tell you which chips you have.
