The ‘SHARPEN’ is sometimes sold as a set with a matching LAUREATE rollerball that featured an identical clip and cap. You can swap the caps between the MP and RB. In this case, I do not have an RB in mint. Let me know if you see one! 
There a marking on the metal reserve tube of the SHARPEN: 9G17A
Based on the shape of the second character, I don’t think the ‘G’ is an ‘8’.
