What are the build dates of the two 'RA' cars? Do you know of HO cars built in the same timeframe?
I went down that trail of thinking too. I noticed that the PHS's I had from the R/A cars had a different format. The 400 car designation was in the middle column and the HO's were in the first column. And then I found this(below) HO PHS which shows the same format as the R/A's.