How do I use a Sekonic Model L-28c Exposure Meter?

Question

It's an old cinematography exposure meter I found. I figured out most of the features, except the inner circle, which has an "H" and an "L". Also, what does the slider do?

Answer 1

I found a company that sells the manual for like $5.99
http://www.mugjoint.com/media/manuals/manuals11.html

Other than that, I can't help you out. Sorry.