It would be far from the first time that such a redesign was implemented to improve coin quality; the 1921 Peace Dollar is a classic example. The Lincoln Wheat Cent is another good example of this design problem. You'll often find them weak near the O in ONE from Lincoln's shoulder on the obverse.
That makes sense lol. It appears to have a similar sort of "die wear" or "melting" pattern to mlov43's coin below, no?
Kinda interesting to see a representation of how metal flows during the strike, isn't it? Theory only, but it's my theory that this is a planchet effect, from the metal failing to become fully "liquid" during the strike. Equally possible is die wear, I guess.
Yes, when it comes to the mushy pagoda eaves, and also not filling in the high relief of the die. And yes, it seems that the scratchiness at the center of the denomination looks to be die wear. After an initial look at the "coincident real estate" on the other side of these 1966 10 Won coins, it seems that the high relief of the pagoda eaves and the relief of the numeral do not match up on top of one another. The eaves are on top of the word "KOREA" with some overlap on the "1". This makes me think the scratches on the numeral are die wear.