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NPCs that can offer Trade Updates:
Arms Dealer
Inventory item traders (e.g. Food Merchant or Black Marketeer).
License broker
Mechanic
Recruitment Officer
Ship Dealer
Non-hirable station crew, which are working on a station (Defense Officer, Engineer, Manager or Specialists) - typically found on Administration platforms. By "working", I mean generally hanging around in bunk rooms chattering with random passers by 
NPCs that never offer Trade Updates:
Architect (even if they are working on plot-rated NPC CVs)
Captain
Marine Officer
Pilot
Station crew if they are available for hire (Defense Officer, Engineer, Manager or Specialist).
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