these:
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Those are the best. IBM introduced this line in the 1930s, equivalent to 3B & 4B at the time, for use strictly with IBM’s scoring machines. Later on, they referred to them as Mark Sensing and stopped using the 3B & 4B identifications. This name change (rebranding) was likely because many people at the time regarded these leads as 6B, including my late friend, Jim Stauffer, who had many of his Autopoint pencils featured in the Century of Autopoint by Jonathan Veley. Jim is the one who introduced me to Jon Veley a long time ago.
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Need any? I have traded with JV, although I did not trade a very early AP to him despite a couple of dangled leadholders…Nice guy, he even posted some pictures of stuff I sent him and I got some nice kudos for sharing…As noted, a great guy…I think his daughter is doing some of the lead stuff with him…not sure , though..
Cheers,
D
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Thank you very much. I have a stockpile of Mark Sensing leads for the next 50 years, if I live long enough.
Jon is a nice guy with excellent manners. Jon posted about the lot of leads he purchased. The info is in the Century of Autpoint. Jon bought a leftover stock from the Panda company and is also generating new leads from unusual thicknesses. I doubt his daughter helps him with the leads. I think I saw once that she published something about Jon’s work. I think her work is related to writing and/or publishing.
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perhaps this 1998 patent can interest you
Non-erasable Pencil Lead
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The link doesn’t open, but I thinlk this is the patent you are referring to:
(https://patentimages.storage.googleapis.com/c5/c9/bf/fc41618397e2a1/US5716434.pdf)
or in 1995:
(https://worldwide.espacenet.com/patent/search/family/016748280/publication/JPH0959556A?q=pn%3DJPH0959556A)
You laso may want to check this link, probably Pilot preceeded Mitsubishi for a similar/same petent in Japanease lamguage:
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For the future, the PDF access to the ppubs expires after a while. Only sharing the patent number works better
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If you ever sell any I would be interested…6B would I guess being similar to JV’s Wet Noodle leads that I primarily use 
What type of pencil you would like to use with these leads?
Do prefer a pencil with an eraser or without? Slim barrel or oversized? 1.18mm thick or 1.9mm leads?
The 1.9mm is used without sharpening, that’s why 1.18mm is more popular.
Depending on the pencil you use, I will tell you which brand of leads is convenient.
In general, the 1 3/8” tall are convenient for slim and oversized twist Autopoint with a grip or short spirals from Autopoint and Dur-O-Lite. Longer leads are convenient with long spirals or Scripto long lead pencils.
Hello…TY for responding, MP wise it would be Autopoint, Legendary Leads (or JV), Parker Vac-Dufold, Wahl-Eversharp and similar brands as I have quite a few…all 1.1mm.
I reckon the 1.9mm would be too thin for the 2.0mm lead holders?
Really enjoy using the softer leads 
Does this help?
The 1.9mm fits the 2.0mm perfectly! But it is short and difficult to sharpen. I use it without sharpening but not with Leadholders, I use it with Autopoint checking pencils.
