About the Veritas Optical Center Punch:
After you have carefully marked your spot, place the punch base and optical post over the spot, adjust it until the crosshairs on the 8X magnifying post are exactly on the mark, then replace the post with the A-2 hardened steel punch and tap the punch with a hammer. A high-friction O-ring in the gold-plated brass base keeps it from moving during this exchange, ensuring near-perfect accuracy. It is simplicity itself to use. As an added bonus, you can use the 8-power optical post as an inspection monocular in your shop. It has excellent depth of field and is easily focused freehand.
Here's where you can get the Veritas Optical Center Punch.
Here's a different brand of Optical Center Punch that comes with the two spotting lenses, TWO hardened steel punches (one 60° and one 120°) and a fitted wooden case. Nice! (I found this one in Amazon's Industrial and Scientific section.)