[docucentre7] Personally, I think it’s the hardest to get in the Pentel High Polymer range. Even if I research it, it doesn’t hit one piece of information. Pentelu (Japan Stationery Age) Purple Red 1.1mm
The original Pentel 11 (about 1967-1971) was released in 0.5mm, 0.7mm, 0.9mm & 1.1mm. There may have been other 1.1mm Pentels, but that is the only one I know of.