Small Tool Identification

[killian6pk]

In cleaning out my fathers house I came across a scriber (my best guess). It looks like a plastic ball point pen, but instead of a pen ink cartridge it has a cartridge with a very sharp pointed metal tip. It has a pocket clip and a push button top just like a ball point pen. It has Snap-On and STP7 Printed on the plastic barrel. Does anyone have a clue. Don't know how old it is or where my dad got this from or its purpose. Thanks for any help.

[snapmom]

http://collectingsnapon.com/catalogs/ca ... gPage=3029

[killian6pk]

Thanks for the Link. Item H is what I have. I would have never pegged it for a spark tester though.