Niewmismatic Error Coins

Strike Through Error On A Malaysia Commemorative Coin 1980
Rarity:RRR
In any manufacturing process there are bound to be mistakes made. Both human and mechanical errors occur on an irregular basis, resulting in defective products. In most industries these bad parts are caught by quality control inspectors or by the persons responsible for packaging the finished products. When spotted, these rejects are simply destroyed. If they succeed in eluding detection, the customer who receives the erroneous part will likely return it for a refund or exchange. But what happens when the defective item is money?

ONE RINGGIT (COPPER-NICKEL) COMMEMORATIVE COIN OF 15TH CENTURY OF HIJRAH-1401 HIJRAH.1980

Struck Through Errors
What is a “strike through” error? Simply put, it is anything which is struck into the coin, but which was not “retained” in the strike. If the item was retained, it would be termed “struck through and retained (fill in the blank).”
Coins have been found struck through buttons, wire, grease, plastic, tape, cloth, washers, sanding paper, other planchets, struck coins, foreign coins, fragments of other coins, springs, and numerous other things.

Where do all these things come from so that they can be struck into the coins? Well, the mint’s are factories, with lots of equipment made up of thousands of parts, machines dripping grease, bolts, screws, and random debris, and so there are lots of things which could break off, come loose, or accidentally be fed into a press striking coins.
One of the most important things in a strike through’s collectibility is if the item or substance struck into the coin can be identified. Most of the time this is easy, but it can also be difficult since things struck into the coin have a habit of getting badly distorted by the strike. If it cannot be determined, it falls into the most basic and uninteresting description “struck through”, which means that the coin was struck through something, but what is unknown.
In this case, it was a piece of wire!

http://dniewcollectors.blogspot.my/2013/11/1969-50-cents-strike-through-error.html