[Lucas00]

To my knowledge staedtler does not make a permanent fine tip silver marker. Emphasis on permanent.

I have read reviews saying their standard silver marker is quite thick almost like a paint pen. That's personal preference if you like a thick or thin autograph.

Assuming you care about the "permanent" claim like I do.
I personally would go with a fine tip silver sharpie. If not staedtler is a great brand and I'm sure they will come out well.

But if you ever want to get a standard card signed with blue marker or really any color. Use the fine tip staedtler lumocolor permanent markers. They are by far the best.