Lining up die on heat plate

Guesstimate one time.
From that measure the result and learn your zero point.
Sorry I can’t be more precise but there’s a slant in the chaise at the gripper bar. One sixteenth inside of the slant is my zero. Alternatively I’ll subtract 1pica 8p from the inside of the chaise to my point. ( If I’m doing a score at 36P I’ll drop in furniture 36P minus 1P 6 plus a couple/few points.)
There’s a line scribed/formed in my chaise .25 below the bottom which is pretty perfect to my guides zero.
It’s simpler than described to me.

Is that just a spare gripper bar there using in the video or something special? Looks like a piece of mylar is placed it the gripper device then on mylar there a printed square that the print is lined up to???

Heidelbergs, whether platen or cylinder, came with pre-positioning devices, for the platen called the Speedy Form Positioner. See “Heidelberg Hints for The Pressman” available for download online in various places.
The chase has a pair of holes, and the pre-positioning device has matching pins, a hinged bar, and a transparent sheet (like mylar). With the first form in position, ink with a brayer, lay the mylar on the form, use brayer or planer to transfer ink to mylar. This is then used to register successive forms.
For my cylinder, I’ve added additional pins to the hinge so I can locate master layouts for specific jobs, adding a standard litho pin-register system to different letterpress chases.

This is what I’m looking for never got one with used press;( could you help me with good pics and measurements? Where u located? Im in Indiana.