The Mizuno MP-20 lineup of players forged irons evoke the classical shapes the company has been known for while mixing in new technologies it’s discovered and pioneered along the way. But the most interesting element in the new design is something that’s a throwback from the 1980s. And no one’s entirely sure how it works, just that it makes this family of irons hearken back to a design technique and a feel that’s more than three decades old.

Debuting this week at the Open Championship, the MP-20 lineup includes the classic muscleback blade MP-20, the mixed material, titanium slugged forged cavity back MP-20 MMC and the hollow, tungsten-enhanced MP-20 HMB. All are fundamentally different, yet each can be mixed and matched as part of Mizuno’s focus on custom fitting and optimising an iron set from long to short. But for all those differences, the subtle similarity across the board is a renewed search for feel.

In the past for Mizuno, that search focused on the foundational steps in iron design, including special varieties of forged carbon steel or unique forging processes. Now, however, the team at Mizuno is going after feel by looking at the last step, the way the irons are chrome plated. And where they started looking is a legend of the past in the company’s more than century-old history.

And that secret is barely one-tenth the thickness of a human hair.

The MP-20 lineup’s secret element is a chrome plating technique that dates back to a legendary set of Mizuno blades developed for the Tsuneyuki “Tommy” Nakajima, who won 56 times over five decades. Brought to market in 1987 in Japan as the TN-87 and in the US as the MP-29, these irons used an underlayer of copper to enhance the usual double nickel chrome plating.

“The urban legend was that it gave it an incremental softer feel,” said David Llewellyn, director of research and development. “It was something that we never really revisited. And some of us were sceptical, how could this have a profound effect on the feel, so we decided to test it.

“But when we ran the blind test out on tour, it was unanimous that the version with the copper underlayer felt softer and better. Even standing behind the player, even with your eyes closed you could hear an ever so slightly more muted sound. There’s something there. Copper is definitely a softer material than nickel and chrome, and you don’t need a whole lot of it to get that feel because it’s actually the thinnest layer in the plating process.”

While that element of feel is a vital criterion, it is not the entire story of the MP-20 lineup by any means. Building off the thinking of its MP-18 predecessor of two years ago, the three parts of the MP-20 are meant to serve both as complete sets of their own as well as an a la carte menu for customized sets. The forgiveness factor increases as the options move from the standard MP-20 blade to the MP-20 MMC cavity back and then the MP-20 HMB, which includes hollow long and middle irons.

The MP-20 forged muscleback blade incorporates a channel in the back that allows for the upper part of the blade to taper through the set. That shaping allows for more weight to be placed higher in the short irons to better control trajectory and spin. Like its predecessor, the heads utilise Mizuno’s “grain-flow forged HD” technique, where the grain structure is most concentrated in the meat of the club.

In the MP-20 MMC, Mizuno again created more forgiveness in a traditional forged cavity back design by forging lightweight titanium into the back cavity, a concept it’s been perfecting in iron introductions over the past decade. This latest design utilises two different titanium pieces to allow the long and middle irons to have a slightly wider, more forgiving sole and the shorter irons to have a slightly narrower more workable sole. This provides a cleaner flow in center of gravity location through the set, Llewellyn said. The MP-20 MMC again utilises tungsten low towards the toe on the long and middle irons that combines with the lighter titanium muscle piece to provide more stability on off-centre hits.

“The reason why we do it is we can put the lower density material in the centre and push more of the higher density material out to the perimeter but still maintain that thickness at impact,” he said

Finally, the MP-20 HMB, the most forgiving option in the lineup, returns Mizuno to the two-piece hollow forged iron design model. It is this ever-growing segment of the iron market that Mizuno largely started with clubs slightly under the radar like the MP-H4 and MP-H5 before moving away from it. The MP-20 HMB mixes two kinds of iron designs within the same set, featuring the hollow, two-piece concept in the long and middle irons (2 through 8-iron) and a partially hollow construction in the short irons (9-iron, pitching wedge) to raise the centre of gravity for more trajectory control. The unique construction in the long and middle irons includes a forged chromoly steel face and hosel section joined to a stainless steel body. The body houses twin 12-gram tungsten weights positioned low in the heel and toe. That internal weighting adds stability and lowers the centre of gravity while keeping the soles from getting too wide. Those long irons also exist as a direct replacement in the both the MP-20 and MP-20 MMC.

“You can say the father and grandfather of this iron was the H4 and H5, but there was an awful lot of effort put into this to really make it look like a muscleback,” Llewellyn said. “Arguably, I guess you could say we were a little bit ahead of our time, but I think the consumer is now recognising with these hollow forged models that they can have that aspirational look and have all the playability that they need.”

The Mizuno MP-20 lineup of irons will be available for pre-sale from September 5 and at retail from September 20 for between $A269 and $A289 per iron.