Life Master > National Master?
There are two types of Life Masters that US Chess recognizes. LM = "Life Master". This is earned by achieving five master norms in US Chess competition. Norms in the US Chess rating system are not easy to come by.
OLM = "Original Life Master". This is earned by playing 300 rated games in US Chess competition while holding a rating of at least 2200. This was previously the only way to become a Life Master, before title norms were introduced.