Hi Folks,
An overview of 5160:
https://www.azom.com/article.aspx?ArticleID=6743
 
A good article on how to best heat treat 5160: 
https://knifesteelnerds.com/2019/04/...at-treat-5160/
And where 5160 sits in terms of toughness among forging cutlery steels: 
https://knifesteelnerds.com/2020/02/...-knife-steels/
Ian: You could ask Larrin at Knife Steel nerds when 5160 came into generall usage: 
https://knifesteelnerds.com/
Cheers
Chris