If you come across one that looks to be painted like a porcelain doll , i.e flawless pale skin , having no tones to the skin, and no finer detail such as veins, mottling, milk spots, capillaries, then this is an enhance doll, and really shouldn't be classed as a reborn at all.
A lot more work and time goes into producing a "real" reborn doll, and can take up to a month, or possibly two weeks if worked on everyday.