Table that stores monthly "beginning qty"

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Hi guys, 

Would you please lend me your hand in finding the table that stores beginning qty (and also value) for  inventory?  Basically, i'm trying to replicate the "5.History" tab in Inventory Inquiry.  I've looked into IM_PeriodPostingHistory, IM_ItemWhseHistoryByPeriod, and coming up empty.   

The IM_PeriodPostingHistory has the beginning qty for inventory only on period 01, which might be due to accounting practice.  Where does the History tab get the numbers from??  The near-instant speed tells me it's not calculating, or do we actually have to back-calculate the quantities??  

Ken