For 1985 10 Agorot this is common. Basically this is the first year for the New Shekel-Agora Series. Its seems that in the rush to get these coins out the mint failed to pay enough attention to the quality of the steel used in the dies or how the steel was treated.
Its interesting that you asked this question now since I literally read this article about 2 days ago after researching another example similar to yours but had only a partial ring.