This was used in Estonia. Can anyone ID it? Have any idea as to value? Its a neat looking design for sure.

incuse embossing on dome - positioned just off center: 517 / F {fancy script letter} / 3080 {3088? 3080?}

My e-friend Zoltan knew the answer to this one as he has a couple similar pieces. This is the top piece of a two-part fuse socket insulator. Another part screws into the bottom. Zoltan has a few pictures here: [id=254425622]

Thanks to Zoltan for helping with this. The shape of this one makes it a very hard piece for me to want to part with considering (despite the large growing number of pieces I now have) I specifically do NOT collect mud!