I can find little about this lens. This is a sum of all the data I could find on the web.
The Triplet-5 100mm f / 2.8 is a lens from the Peleng 500A projector for 35mm film.
Last year of production: 1991
Optical design: triplet
Sharpness is not as great as the benchmark Diaplan 100mm 2.8. But it's sharp enough for artistic stuff and works ok as a Diaplan/Trioplan alternative.
Very cheap and standard 42.5 rear barrel.