This is an excellent question! “that PWT can keep on punching above its weight” is a noun clause, and it is an “appositive” noun clause, which means that “that PWT can keep on punching above its weight” renames “it” when you wrote “IT’s as a center of manufacturing excellence”. The “it” is an introductory “it”, which means that it prepares the reader to what comes next in the sentence; in this case, the appositive noun clause “that PWT can keep on punching...” is what comes next. You could say the sentence this way: That PWT can keep on punching above its weight IS as a center of manufacturing excellence. Here, the appositive noun clause is the subject of the sentence; in spoken English, this is not commonly used, but it is used in written English. Writing the sentence this way draws attention. Writing the sentence with the introductory “it” first prepares the reader. I hope that helps.