Crow
Crow Person
Did someone mention hickory? 
The first irons were very crude affairs, blacksmith forged and no two were exactly alike but they were all blades of the simplest type, a flat piece of iron.
They stayed this way until around 1900 when people started to experiment a little by moving metal around in the blade to change the centre of gravity and inadvertently the MOI.
Most of these experiments focused on positioning the added weight behind the centre of the club in the idea that this would give a more solid strike, which indeed it did but at the same time it meant that off-centre hits were even worse.
Over time and much experimentation it was realised that mass lower down in the club head would assist in the launch of the ball and the blade developed into the form that just about everybody used up until the 1970s. Which means that everybody must have been great ball strikers if we believe what we're told today about those who can use blades.
In the late 1960s/early 1970s the first commercially successful attempts at perimeter weighting were made, and Karsten Solheim was one of the true pioneers in this area. His first ventures were in the early 1960s using solid blades and just milling out cavities in them, Google Ping Ballnamic irons for more info. The Ping Karsten 1 was released in 1968 and these were very successful clubs with many copies. These were followed by several improvements and then the Ping Eye and the most successful of all, the Ping Eye2.
Perimeter weighting was a huge step in making golf easier, although the distance the ball was hit was pretty much the same loft for loft, it was just that Ping irons were stronger lofted than many of their competitors at the time.
The next big change was the use of hot faces. These are thinner faces with better trampoline effects that do give better ball speed, I'm not sure when these really took off but probably post 2000. Multi material heads have also been big recently, tungsten weighting etc, but all that is really doing is providing perimeter weighting without it being obvious so the golfer can feel like a "player" with blades. I think it's hot faces that have caused issues with the occasional rocket ball that goes 20 yards longer than usual, and they also make touch shots such as chips around the green tricky as the ball comes off too fast.
So I'd say there have definitely been changes in the last 10 or 20 years, whether or not they're all positive is another matter.
The first irons were very crude affairs, blacksmith forged and no two were exactly alike but they were all blades of the simplest type, a flat piece of iron.
They stayed this way until around 1900 when people started to experiment a little by moving metal around in the blade to change the centre of gravity and inadvertently the MOI.
Most of these experiments focused on positioning the added weight behind the centre of the club in the idea that this would give a more solid strike, which indeed it did but at the same time it meant that off-centre hits were even worse.
Over time and much experimentation it was realised that mass lower down in the club head would assist in the launch of the ball and the blade developed into the form that just about everybody used up until the 1970s. Which means that everybody must have been great ball strikers if we believe what we're told today about those who can use blades.
In the late 1960s/early 1970s the first commercially successful attempts at perimeter weighting were made, and Karsten Solheim was one of the true pioneers in this area. His first ventures were in the early 1960s using solid blades and just milling out cavities in them, Google Ping Ballnamic irons for more info. The Ping Karsten 1 was released in 1968 and these were very successful clubs with many copies. These were followed by several improvements and then the Ping Eye and the most successful of all, the Ping Eye2.
Perimeter weighting was a huge step in making golf easier, although the distance the ball was hit was pretty much the same loft for loft, it was just that Ping irons were stronger lofted than many of their competitors at the time.
The next big change was the use of hot faces. These are thinner faces with better trampoline effects that do give better ball speed, I'm not sure when these really took off but probably post 2000. Multi material heads have also been big recently, tungsten weighting etc, but all that is really doing is providing perimeter weighting without it being obvious so the golfer can feel like a "player" with blades. I think it's hot faces that have caused issues with the occasional rocket ball that goes 20 yards longer than usual, and they also make touch shots such as chips around the green tricky as the ball comes off too fast.
So I'd say there have definitely been changes in the last 10 or 20 years, whether or not they're all positive is another matter.
