As I recall, it wasn't a calibration negative, it was a piece of ND filter gel that you cut into the required number of pieces. So you are doing exactly what the original method specified. You can verify when you get a copy of the manual.
Roger is the person who has the HM device that you linked to above. His email is below the pix of the HM device.
His site shows a picture of the instruction manual, so if you can pay him to copy the manual for you, then you will have the manual.
You could also do an internet search for the manual. But some of those old manuals are really hard to find, especially when it is not a mainstream item. So when you do find them, you have to jump on it. When it sells, Roger won't be able to copy the manual for you. Personally, if I had the manual, I would scan it so it could be easily sent to anyone who needed it.
Now one thing to remember, the HM stuff were kits. You could ask him to just copy the owners manual. But I think it is a good idea to also have the assembly manual. Then you have it, in case you need to have someone repair it for you.
Last edited by ac12; 02-01-2013 at 11:35 AM. Click to view previous post history.