Malaysia Parliament Series 1973 Coins With Collar Die Strike Errors
The collar is a part of the coin die apparatus that holds the coin planchet in place while the coin is struck. On all coins except the 50 Cents coins, the collar applies the edge to the coin during the actual striking, whether the edge is simply plain (like 1 cent) or reeded (like a 5 Cents,10 Cents and 20 Cents.) The collar not onlyholds the planchet in place during minting, it causes the reeded edge to appear on coins.
The 50 Cents coins are being struck differently.The collar applies the edge lettering to the coins before they have been struck by normal means. The orientation of the edge lettering (whether the heads side is up, or the tails side up) is random, and coins with the tails side up when you read the edge lettering are not errors.