The findings are from an excavation carried out at an Iron Age hill fort known as Broxmouth in East Lothian during the 1970s but have not been published until now.
Fresh analysis of some of the artefacts uncovered found they can be dated to 490-375 BC and are made from high-carbon steel.
The ancient relics had been deliberately heated and quenched in water, and are the earliest evidence of sophisticated blacksmithing skills in Britain.
Experts have heralded the discovery as particularly significant as it offers an insight into not only the early development of such advanced manufacturing skills, but also social organisation at the time.
Dr Gerry McDonnell, an expert in archaeological metals and a specialist involved in the project, said: "The process of manufacturing steel requires extensive knowledge, skill and craftsmanship.
"It points to an advanced, organised community where complex skills were refined and passed on."