What are Milled Edge Coin variants actually.... ??

Security Edge ?? Milled Edge ??

Most of the coin collecter have a doubt regarding milled/reeded edge variants for security edge high value coins... Are these deliberately minted ? If yes then how come a coin has partial milled edge and partial security edge ?? Or are these coins some sort of error coins ? And if error why are they listed as variants in Krause Catalog as varaints.... ??

Here is a article which might help u gets your doubt clarified :

Normally high value coins are produced with a 'Security edge' like Rs.2 coins in before 1990s and Rs.5(normal and commemorative) coins till 2008. This is done to check counterfeiting(making fake coins) of coins. Coins having 'security edge' are first struck with the usual upright milling at the time the obverse and reverse designs are impressed upon them same as the edge of milled coins shown in this article . These are next passed through a second press, where the security mark is put on the edge, under pressure.

But, while being fed into the second machine, if a few coins accidentally skip the press, these may go to circulation with normal upright milled edge or if get pressed partially they lead to partial security edge and rest milled. 
Thus we find another type of error in coin specimens with upright milling which should have a 'security edge'.
These are milled edge or partial security edge variants of such coins.

Then the question comes why these are not categorized as error 
coins even when they are actually error coins. The only reason for this is that the number of such error coins having milled edge is large as compared to any other kind of error coins which makes them a variant rather than a error coin.

History of Security Edge... how the term was coined ??

In olden days the coin was fed manually and the impression was hammered.The coins was made of silver and unprincipled persons used to shave the coin near the edges to steal part of the silver. Hence when automatic machine minting came in to use, A security edge was implemented around the circumference thereby proving that the coin had not been tampered with and the weight of the coin remained the same as per the minted coin. Hence this impression around the edges was called security there by securing the actual weight of the coin.

 Some pics of the such variant coins :

Special thanks to senoir coin collecters Sekhar Kausik and Balakrushna Kar who helped me in writing this article.

Note : Not all Milled edge coins are error coins. Recent rs.5 Ni-Br coins 2009 onwards and olden days silver coins had milled edges only.