Mitsubishi’s Hi-Uni drafting series is the elevated version of what I consider to be the most basic style of drafting pencil—a metal knurled grip with a different material on the rest of the barrel.
The Hi-Uni series is noteworthy for at least 4 reasons:
- All models were originally sold with protective caps
- Some models had a unique, finger-press lead advance mechanism (ff)
- Lead size indicator on the first stepdown section of the nose cone
- “CARBO” color variants that created interesting barrel patinas that would change based on sun exposure (I’ve seen red and blue versions; unsure of any others)
The ff and CARBO were elevated features found on pricier models. Also, I think each base sub-model (2050, 3050, 3050ff, 5050, 5050ff) was only produced in 0.3 and 0.5mm variants.
At this point, scoring any Hi-Uni model for under $250 is an unlikely proposition. And a CARBO or ff variant will probably set you back at least $500.
But a red CARBO 5050ff? How deep are your pockets? 
This places the Hi-Uni series in a stratosphere only occupied by a few other noteworthy MP families:
- Pilot H-1000+ — considered by many to be the epitome of “hi mecha” and the most grand MP family of them all (includes 100X, 210X, 200X, 300X, 5005)
- Tombow Variable — the most expensive MP family with a 0.4mm variant
- Faber-Castell TK-matic and alphamatic — classic hi mecha designs with robust materials and ultra-premium color variants
- Pentel Mechanica — oldest and most venerable; we’re not having this discussion without the Mechanica’s existence
Outside of these 5 families, there’s only a smattering of pencils that can claim $200+ per piece.
In fact, I’d argue the existence of these 5 families is precisely why so many other rare pencils have skyrocketed in value. For example:
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Why do people pay $150+ for Newman drafting pencils that exhibit basic “hi mecha” design traits?
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Why is the Platinum Angle (with chevron grip) priced and treated as a hi mecha equivalent?
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Why are cool riffs on hi mecha themes—such as the Pilot Sprinter or Pilot Pro-tex—so sought after by collectors?
Bottom line?
Given enough time, anything hi mecha or hi mecha adjacent is going to be worth a lot of money.
Just look at the Pilot Automac, which now fetches $60+ per specimen when it retailed for half that less than one year ago.
From the current “modern” generation of pencils, only the Pentel Orenznero will reach stratospheric valuations like those that will undoubtedly be seen by the Automac.
And all because they are part of the hi mecha lineage that well and truly drives this entire secondhand market.
). Probably Mitsubishi didn’t want to have the kind of washed-out-look on their poster.