AR, AE, AG in his catalogs are not after each medal. Let's take 97.2 for example. It mentiones AR R2 (in silver rarity R2). No other metals are mentioned. That does not mean that this medal does not exist in copper, it just means that in author's oppinion this medal is common in copper and does not deserve rarity rating. Actually, if you look lower, you will see that copper medal sold in WWCC auction 21.
As a side point, starting with book part 4 author added rarity rating R0 (parts 1-3 had lowest rarity rating R1) to identify medals that are one notch up from common. So R1 is equivalent of RR and R0 is equivalent of R.