In open pit market, it's only 100 guys in the pit and the traders all know each by name and who is trading. some markets even less traders participating. 5 companies are the demand for coffee and copper etc. its a very small market and everybody knows each other. the floor traders, institutional traders, the hedge fund traders, etc. In eletronic market especially hours or even regulators hours you have no idea or know who is buying or selling pit traders used to have an advantage as they had info that most people don't have.
open pit market is when highest bid is always filled and in 'auction' of market compared to ' dealer' market. The NYSE used to a open auction type of market whereas the Nasdaq was dealer quoted OTC market cause it was less liquid and dealers had to put a bid when nobody is willing to bid. commodity markets .or blue chip stocks or bonds ..it always has a bid as it has 'value' where stocks may not have value. ie options and penny stocks are too illiquid for an auction market. you have no real bid. other than market maker or dealer quotes.. some stocks only have one dealer obligated to put a 100 share at the bid and 100 share at the ask. you need one market maker for listing. requirement.