Casting anomalies - flaws in the mould?

G’day folks - this article in the current issue of eNAMEL Online
Newsletter contains an exercise in simple logic based on observation.
Were the deficiencies in the casting pictured in these pages caused
by flaws in the mould? If they weren’t, what did cause them ?

http://users.netconnect.com.au/~enews/

click on the link “Casting Flaws ?” or the picture in the right hand
navigation column. I’d appreciate assessments of the problem from
the Orchid community.

Thanks, Al Heywood