The first three characters of an iPhone panel serial number name the company that made the screen panel.
Short answer: GH3 is listed as LG Display. Confidence: confirmed (at least two independent sources).
An iPhone's diagnostic file (sysdiagnose) holds a panel serial number. Its first three characters are the panel code. Sources report that a panel starting with GH3 was made by LG Display. They report it for: iPhone 15 Pro Max, and the 16 and 17 series.
Read all three characters, not only the first letter: the letter G starts codes for both Samsung Display and LG Display panels.
This page does not say one maker is better than another.
Sources list GH3 as LG Display. Confidence: confirmed by at least two independent sources.
This page does not rank makers. The code only names who made the panel.
No. The code is only the first three characters. Panelmi also shows an approximate month decoded from the characters after it. That decode is a working assumption, so Panelmi always says "about".
Panelmi shows "maker not identified yet" for a code it does not know and lets you send the model and the three characters so the list can grow.
How to share an iPhone sysdiagnose · All panel codes