Commonly called mechanical pencils, these make sketching or writing in the field clean and easy. Leads can be inserted into either end, just slip the ring down to tighten around the lead. These are handmade out of brass.
Small: 4" long - single-sided lead
Large: 7" long - double-sided lead.
Still use this almost daily in my drawings. I love it so much it actually motivates me to draw more because it’s so cool.
Nicer product than ones I've seen on other sites. The flush rings make it comfortable to hold. Extra leads would be nice. I didn't see any on your site.
For late 17th century events it's the perfect entertainment for my 7 year old son and very useful when I need to take notes.