Hello USER500....my boss from a previos job (he owns a boutique and he's the buyer for his own store) told me that size SS from Comme is only available to the Japanese market.
I'm not sure what year size SS was started or manufactured.
As with current fashion.....silouettes are now much slimmer, lean, and small. But, back during the 1980's, proportions and sizes were much bigger and deliberately exagerrated. Back then, wearing baggy clothes was more in style, especially very large shoulders. Older collection.....dating from around 1980-1990 from Comme, tend to fit quite big, even in a size small.