I have a magen david with שוי writen inside and I want to know the meaning
Could it have been ש - ד - י, and the tip dalet got scratched off? This name of God is often found on a mezuzot.
Maybe it is initials of the original owner?
I agree with the already posted answers & comments that a picture would nice, that it may be a dalet rather than a vav, and that it may be the owner's initials. If it is a word שוי, then the only words I can think of with that spelling are:
- sh'vi, the feminine singular imperative of "to be equal" or "to be worth it" (shin-vav-he in kal), and
- shevay, "that woe!" (as in a sentence, "he agreed that woe for the loss").
Not that either makes much sense.