Does any one know what this is?

Hi this this is my first time posting on this forum.
I found this in my house the other day and couldnt figure out what it was. I think it might be a pen of some kind but have no idea the tip does retract into the case and both the tip and the top unscrew. I also know it is sterling silver it also has a stamp with an S on it and a face of some kind. And on the top their is some sort of jewel with i think someones initiels, which i think are a backwards R and B .Would be a great help if any one has any info.
thanks matt
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What you have is a silver propelling pencil.
It could be dated from around 1880 - 1920
It looks Victorian to me.
With out seeing the hallmarks I can’t give you much more info,.
Value around £20 -£30
Try searching on eBay for "Victorian silver pencil” to see other examples.