My Comments as Advocate
This is a great proposals but let me suggest a few things.
Think about removing these three temperature terms to simplify and better understand the citation. Limiting yourself to the discovery by Chu and his seminal patent qualifies as a milestone but I didn't like your citation because it is too similar to the existing 1911 Milestone on Superconductivity eg " makes many electrical technologies possible, including Magnetic Resonance Imaging MRI and .....".
Scope of your proposal: More importantly think about nominating and awarding the entire HT superconductivity lab or research effort as a milestone, not just the discovery of one particular material by Chu. Now I am not an expert, neither do I know what UH R&D facilities did, by who, when or where. But something concrete was developed as a result of great works at the lab: ( a flat HTS wire) by Researcher Venkat Selvmanickam which lead to the execution of an agreement with SuperPower and UH. I consider such an agreement a milestone which unfortunately for you may not satisfy the IEEE 25 year rule. Anyway, what I'm trying to say is that you consider broadening the scope of the milestone to encompass High Temperature Superconductivity research at the lab leading to the Chu discovery and all the other great works leading to the development of superconducting wire. Take a look at HTS lab/research/staff/ as a whole project instead of focusing on just one discovery. Then it becomes the UH HTS lab instead of Chu. This is just my suggestions. Perhaps other milestone plaques will adorn the halls of UH one day.
More backup references are required, i.e five.