This is just an attempt at describing what the names "Pro" and "MP" used to stand for in the Head racket lineup, and how their use has developed over time. As I was away from the game during the latter part of the 90ies and until about 2010, I have some large holes in my knowledge as well, and maybe more knowledgeable guys (such as VSBabolat) could chime in here.
But anyway, here we go: In the late 80ies, Head had the "Pro" in the Prestige, Elite, and Elektra, all three were "Mid-size" rackets with what Head proclaimed was a head size of 600 cm², which corresponds to 93 in². Of course, we all know this is not the correct head size, but the best bet is that Head picked this number because of marketing reasons, as they soon released rackets with head sizes of 660 ("Master") and 720 ("Director") cm² (the names Master and Director had been used before that time as well). This was in the late 80ies, when they hastily developed their first widebody frames, which had come into fashion at that time, mainly because of the new racket tech invented by Siegfried Kuebler. The Elite and Elektra received what was called the "Double Wedge" technology, which is actually pretty much a beam construction like the current Völkl V1 Pro (taper at the top and just above the handle). But the Prestige Pro didn't receive the Double Wedge treatment, and a Prestige Master wasn't introduced until a little later, while the Elite and Elektra lines quicky faded away, to be supplanted by other DW lines - the early 90ies saw some thick rackets from Head, but also from all the other companies (e.g., Prince Thunderstick). Again, the Prestige Pro stayed for good, and nothing was changed. Then, I think Head got into some legal fight with Wilson, and was no longer allowed to use the name "Pro", but I am not completely sure about this being the sole reason!
Instead, Head renamed the Prestige Pro the Prestige "Tour" 600 (which also got a completely different handle technology, the suspension grip; these rackets have a much shorter hair pin and the handle is separate) and also offered the Prestige "Classic" 600, and then "Classic Mid". A Prestige Tour 660 (Master category) was also introduced, which later would be labelled the Prestige "Team" (FlexPoint and MicroGel generations). So the "Mid" entered the scene. Also, when Head snatched up Agassi, they developed a copy of his trusted Prince Graphite Oversize (without the cross-bar), and labelled this new racket the "Radical". Head came up with some new numbers: The Radical Oversize was claimed to have a 690 cm² head size, and while they were at it, they also introduced the "Mid Plus" head size, which stood for 630 cm².
The Radical Tour MP (yellow-black) and the Pro Tour MP are the two ancestors of the Prestige MP; they both had the same mould (head gave it the number "57"), and while the Radical received a new mould with the Titanium line, Head continued with the Pro Tour 630. I think a Ti.Pro Tour was also offered for a short time. By the way, Head also made a Pro Tour 690, same mould as the Radical OS. But back to the MP and Pro issue. - The Pro was absent from Head's lineup during that time, and because the Prestige Mid had a 18x20 string pattern, the larger Mid Plus also had a 18x20 pattern. Noone at Head was thinking about a 16x19 string pattern for a Prestige (or Pro Tour, or Radical Tour) racket at that time, neither for the Mid, nor for the MP.
Then, Head decided to abondon the Pro Tour MP when they went intelligent, that's when the i.Prestige came out. This was basically a consolidation of the separate Prestige (Mid) and Pro Tour (MP) lines. Note that the i.Prestige MP still has the same design code (57) as the Pro Tour and the Radical Tour, the suffixes (most populat: A and E) stand for different degrees of flex/stiffness.
And then Head embarked on their now well-known cycle of introducing new technologies roughly every two years. But when the successor technology to the i.tech came - the LiquidMetal tech -, Head also changed the mould of the Prestige MP. It still was congruent with the former mould, but the ridges in the throat were absent, probably because of the LM ridges in the inner hoop. Same goes for the FlexPoint Prestige MP, which is just the LM Prestige MP with the FXP holes. I think that mould has the number "224".
For the MicroGel Prestige, Head went back to the original design, but the mould was still changed in some places, leading to the number "238". And now they also made a Prestige "Pro" again, for the first time offering a 16x19 string pattern in the Mid Plus head size. Seems like the "Pro" name was available to Head again, and the traditional MP had the 18x20 pattern, so there was no need to change that. Plus, I think the 16x19 string pattern had already been in use by some pros, so this made sense.
For the Radical, Head had been offering a "Tour" version after they had changed the mould of the MP: The LM Tour was the same as the LM MP but with different specs (heavier etc.), and the FXP Tour received a total redesign, the Tour now was 645 cm² (100 in²) and also had a 16x19 string pattern. The Radical Tour became the Radical Pro with the MicroGel version (still 645 cm²), and the YouTek Radical Pro also had a 16x19 string pattern in a 645² head size (I'm not detailing all the mould changes for the Radical line here...).
So Head had it nicely balanced but actually only until the YT generation because that's when they signed Djokovic and had him promote the Speed line. Problem was, Djokovic was and still is using an old Radical MP mould ("113") with an 18x20 string pattern, so the Speed Pro got 18x20 while the MP got 16x19.
Now the racket lines were no longer in sync with regard to the combination of "Pro" and "MP" with "18x20" and "16x19". The next few years would see Head radically change the Radical for the YouTek Graphene generation, eliminating the 18x20 pattern from this line and also stepping away from the constant beam design for this line. And while they were at it, they also changed the Prestige Pro by using the same mould as for the Prestige S, which had been introduced with the YouTek Innegra generation. This mould is a little thicker (22 mm instead of the 21 mm the MP/Pro had been before - which actually is really 20 mm...) but other than that, I don't know much about it (I have never played with a racket of this mould).
Starting with the Graphene generation, Head's Prestige Pro is therefore no longer the same racket as the Prestige MP only with a different string pattern (and probably some variation in the design of the flex of the racket). So far, Head has not changed the Prestige MP. Its current mould is the "293", indicating it received another minor tweak from the previous 238 mould. But other than that, the Prestige MP is basically still the old trusted Pro Tour MP, albeit with different ingredients and - as many experts will emphasize - different playing characteristics.
- I gotta go now, hope that all of this has some explanatory value. It certainly needs to be enhanced with more details, especially in the latter part...
