this is just a guess from looking over the blurbs on greatmodels,
but it seems that 6040 included some PE.
its description is: "Rotating turret/ photo-etched/ Hi-tech w/ 483 parts. New tooling"
this kit is discontinued (tho still available)
the description for 6136 says nothing at all other than 'reissue'.
since they show a retail of almost $36 for 6040 and the newer 6136 is $29,
i am guessing they dropped the PE bits.
ed.