This is the smallest knife available on the conservation market, with a .9mm width. The M2 steel blade retracts into a standard supplied mechanical pencil handle, so it can be retracted when not in use. The blade can be extended to about 20mm to reach into recessed areas. It has a double bevel, and can be used for cutting complex fills, working under magnification, miniature bookbinding, anywhere you need to make precise small cuts. Can be resharpened and stropped. Or the blade could be dulled to use as a micro spatula. The M2 steel blade is hardened to Rc 65. Just don’t mistake it for a pencil!
Order a .9mm Micro Knife with retractable mechanical pencil handle here for $35.00.
Peachey Conservation 
Does it completely retract into the pencil ?
Yes, you have to press the button at the top of the pencil, which releases the brass clutch inside the pencil. Then press the blade into something soft like leather or wood until the blade is covered.
This is so wonderful! I am working hard at thinking of a way I could justify purchasing it. ; ]
Justify? What? I’ve always assumed purchasing books and tools need no justification!