Never saw a Leather Harrington in the 60s just like i never saw a Barracuda, The only Harrington I remember was made by Sky Jump, Most of us had three of four, Once Skinhead dress became popular..you could get all sorts of kit from the markets. So maybe one of the sweatshops down the East End made leather Harringtons, ??????
I think once the harrington became a popular item (and it was very popular with skinheads!), other versions came along - more obscure coplours, dogtooth, Prince of Wales, Tonik, cord, leather, suede, tartan. Another regional thing but some of these became popular, some never caught on.