I was looking at someone's mezuzah today. Here is an image of part of it:
When I looked closely at one of the words I saw roshem that looked like something had been erased in between the ל and כ. Here is a close-up:
My question is: Not knowing the source of the mezuzah do we assume that the erasure was before the כ was written and it is ok, or do we assume that it was afterwards and therefore passul?