US Banknote Catalog Number Assistance Needed

I've got a US banknote that I'm thinking about sending in to get graded by PMG.
The form asks for a catalog number. I don't own any price guides / catalogs as I don't really have a large enough collection to justify the purchase.
I was hoping someone on here might be able to help me out. I'll even say pretty please if it helps, lol.

The note I have is: Unites States $50 1981 G (Chicago) Star
It's a fairly scarce note. There were only 128,000 printed.
This is the note I'm talking about (image is mine): 50 Dollars (Federal Reserve Note; small portrait) - United States – Numista

Nevermind. I found it with a little more digging around. On the PMG website they have $50 and 50 Dollars. They are not the same apparently.
I also found a different catalog number in their census.
So the question is, do they want the 2120-G* or the 472a?

I checked myself and only found P#472a.