Seam on porcelain

Hello girls :-)

a short time ago I bought a doll from Lutsenko-Dolls. Some may remember my Lilliana ;-)

I have examined her very closely and I saw that she has some strange "seams" on the outside of her legs and arms. They are difficult to photograph but I tried nevertheless. Do you have these on your dolls also?
If an artist is reading this: Could you explain how they developed through the process?

1.) On the lower leg, quite in the middle

20151006_203637 by Diana Hinkelmann, auf Flickr

2.) On both lower legs, right in the middle

20151006_203908 by Diana Hinkelmann, auf Flickr

3.) On the hip-joint and upper leg

20151006_203839 by Diana Hinkelmann, auf Flickr

4.) On the arm quite near the hand-joint and on the hip-joint lower then middle.

20151006_203803 by Diana Hinkelmann, auf Flickr

5.) On the kneejoint (lower then middle) and lower leg (middle)

20151006_203646 by Diana Hinkelmann, auf Flickr