Hey PaulKirk! Chances are, the lower resolution comics were scanned from something that was less quality. Often the condition of what we have in the archives is subject to the wear and tear of history. There’s a lot of what happens in the comic world that replicates the art world- things are stolen and black market swapped, and sometimes the highest condition items are just not available.
We do have a bit of insight from a previous Q&A with our archivist Ben LeClear, and we hope to have them back in the near future to talk more shop 