Copolymer purity, what does AN / MA / MS mean? I would like to buy some polyacrylonitrile (PAN) powder from GoodFellow and I have the choice between these two products:

AN316010, quality : Copolymer (99.5% AN / 0.5% MA)
AN316020, quality : Copolymer (93.9% AN / 5.8% MA/ 0.3 % MS)

What I do not understand is the meaning of these three acronyms. What is the abbreviation hidden behind AN, MA and MS?
This may be an obvious question but I was unable to find any answer so far. I guess this may be somewhat linked to a certain degree of purity of the product, but since polymers can also be sold with different Monomer / Polymer ratios, I wanted to be sure...

My best guess for now is that AN may be AcryloNitrile, but I have no idea as for MA and MS... MA may be Methacrylic Acid, but could also be Methylmethacrylate Acrylonitrile or Maleic Anhydride (see here). Any help to answer this question is more than welcome.
Although in this particular case I may simply contact the supplier to have my answer I also wonder:
Is there a general way to solve these chemical identification issues or is it up to each supplier to name these types of compounds as they see fit?
I contacted GoodFellow directly and they gave me the following answer:

93.9% AN: 93.9% AcryloNitrile
5.8% MA: 5.8% Methyl Acrylate
0.3% MS: 0.3% Methyl Sulfonate

I guess different manufacturers may name their products as they see fit. In particular, for polymers that can share the same abbreviations, only the context and a good background knowledge of their synthesis pathway may allow one to decide...
There are, however, IUPAC guidelines for polymer abbreviations available here[1]. In addition several other websites offer their own abbreviation list e.g. here and there.

[1]. J. He et al., Abbreviations of polymer names and guidelines for abbreviating polymer names (IUPAC Recommendations 2014), 2014. DOI: 10.1515/pac-2012-1203