Machine Doubling occurs during striking of the coins and is very common for coins of many countries due, in part, to the sheer number of coins struck. I have at least one coin from Singapore with Machine Doubling. I'm not an expert on coins of that country, but for most coins of other countries machine doubled coins are not highly sought and/or so common that they are not valued any more than a regular issue coin without Machine Doubling.
I too had a hard time distinguishing Machine Doubling from true dd's. I found it helpful to search for good photos of true doubled dies and compare them side by side until my eye could readily tell the difference. Machine Doubling is flat while true dd's are very rounded. Hope my two cents helps!