1986 Jefferson 5 Cent Struck Through?

Hello,

I am not really clear on what a ' Struck Through Grease' coin looks like. To the best of my understanding, this results in non-existent or 'mushy' devices (I think that's the word-still learning the vocab.) How do you know the difference between a weak strike and a coin struck through? This nickel looks unusual to me. It has a lot of luster and the reverse is in good shape; however, the obverse looks suspect. Any feedback on what is happening here would be appreciated.

Thanks,