Arsenal Istimewa baju bolasepak 1982 - 1983

1982 - 1983 Arsenal special baju bolasepak. I can’t find a shirt like this anywhere on the internet and have never seen one like it before. There is a label (pictured) that says: “Umbro R&D Sample”, so my guess is that it’s a prototype that never went into mass-production. I THINK it's from 1982/83