Is there a din regarding the amount that the shin must be embossed above the bayis? One of the lines on the shin got chipped, so if you were to look at it from the side, you would see a dip in the middle of the line, but there is still a tiny amount of thickness.
Technically it is still kosher. The sin has to stick out, but there is no specific amount of height that it has to be sticking out. Practically though, upon the advice of R’ Gitman shlit”a (author of Zichron Eliyahu on the making of batim for teffilin) the teffilin should be seen by a batim macher, and someone who understands these things well.
Shulchan Aruch O:CH 32-42, Poskim