[Gurps Fan]

Delvers with Occultism can:

• Detect curses, if there is a visible cursed object (altar, idol, etc.). (DF 2, p. 9.)
• Analyze curses. (DF 2, p. 9.)
• Recognize wierd monsters (like "Spawn of 'Thulhu"), adding some useful informations (favorite weapon, special power, weakness, etc.) with margin of success 2+. (DF 2, p. 9.)

Delvers with Hidden Lore (Suitable Specialty) can:

• Recognize monsters with complex hierarchies or cultures (like demons, elementals, undead, etc.), adding some useful informations (favorite weapon, special power, weakness, etc.) with margin of success 2+. (DF 2, p. 9.)
• Reveal disadvantages (Dread, Fragile, Revulsion, Susceptible, Uncontrollable Appetite, Vulnerability, Weakness, etc.) that the monster possesses. (DF 2, p. 10.)

Thus, indeed Occultism and Hidden Lore are both "monster knowledge" skills, but Hidden Lore can reveal monsters' weakness that adventuers can exploit more precisely. Even if a master of Occultism makes his skill roll by 10 (= five pieces of information), the GM can always choose to hide his monster's weakness by giving five pieces of non-combat information. Against a practitioner of Hidden Lore, the GM has no such countermeasure; when a delver with Hidden Lore gets a margin of success 10, the GM must tell five disadvantages.