It's probably a bug that we are generating solr_marc.jar into lib/ in the first place. 

It means that if Blacklight updates it's bundled version of solr_marc.jar, and you update Blacklight in your app -- you'll nevertheless still be using the solr_marc.jar that was generated into your app. 

When I wrote the solr_marc.jar stuff, the intention was that ordinarily an app would use a solr_marc.jar directly from the gem, so if the gem updated it, the app would be using the new version. _Optionally_, if you wanted to use a solr_marc.jar differnet from the one bundled with Blacklight, you could put it at 'lib/solr_marc.jar` in your local app -- say if you needed to use a newer version than the bundled one, or one compiled with a bug fix that wasn't in the bundled one yet. 

And it used to work that way. 

At some point after that, literally a couple years ago now, someone misunderstood the intent and changed the generator to always generate a solr_marc.jar into your local app. 

I've mentioned it several times, but havne't had time myself to actually figure out what's going on and fix it, and apparently nobody else has had the motivation either. 

But if you are working on this stuff at all, please consider making it no longer generate solr_marc.jar into the local app, at least not as a default. That was not the intention, and is harmful, as it will keep many local apps on old buggy versions of SolrMarc, even when new versions have been released and bundled with the relevant gems and the app has updated it's gems etc.