773$x should be an ISSN index.
I am not sure what Nicole meant here, can someone help?
I assume she meant that we should add the field to the ISSN search index. But I see some problems there: It would give you many more results when searching by ISSN in databases that include article records. What about other 7xx fields? I believe as proposed this would be a bit problematic, but maybe we could imagine having a separate "wider ISSN" index?