Cheers - think I found my answer at Corsair Support (House of Help) :
CM2X1024-8500C5D/F
........................XMS850X v1.X...MICRON.........64Mx8...Rev.D (2.2 Volts)
........................XMS850X v2.X...Qimonda........64Mx8...70Nm (2.1 Volts)
........................XMS850X v3.X...Elpida............64Mx8...(2.2 Volts)
........................XMS850X v4.X...PSC..............128Mx8 (2.1 Volts)

TWIN2X4096/CM2X2048-8500C5DF
........................XMS850X v1.X...PSC...............128MX8

I have 2 sets of CM2X2048-8500C5DF = 8Gb - they run fine @ 1066. Have not tried to OC yet as I have a Phenom Black Ed.