https://www.investopedia.com/terms/a/afterhourstrading.asp
I also understand that a market participant may arrange with their broker to execute a transaction immediately after the close based on the high of the day, the low of the day, or the average price during the day.
How any of this fits into what happened with LBSR yesterday, I don't know because the after-hours trade was lower than the price at any point during the day. And, given the history of these after-hours trades in LBSR, non of it appears to be news-related.
Does anyone else have any other observations on this topic? BillCPA? WillyB?