To me it looks like typical signs of balsam separation - very early stage though - lens still is usable but really can't be described as faultless I think . Lens separation looks like there was something leaking inside the glass , with feerie colors - kind a like oily stains on a water with shiny reflective surface when looked at from a certain angle - but often not visible when looked at from another. Lens with this condition should be still fully usable and capable on APCS - and even on full frame the degradation will probably be minimal, and only in flare/contrast plus only at wide apertures probably. I wouldn't worry too much - I myself have a lens 85mm f1.8 that will never sell and it has serious balsam separation - still produces awesome shots
--manntax