Every circumcised penis has been scarred... It marks where the two cut edges of the foreskin stump were crushed and mashed together. The Plastibell method of circumcision leaves a more prominent and darkly colored scar. Other methods leave a jagged, uneven scar*. ... The section goes on to say that the darker your skin the more noticeable the scar.

* I could immediately tell that my newborn nephew had been circumcised with a Gomco clamp because the scar line where his foreskin was removed was jagged and uneven, just like the book mentioned.