If they're classical and opera, very few people want them. The old 78 rpm recordings needed a a couple or more discs to record a symphony, operas needed even more, so they were packaged in book format albums with envelope pages for each disc. (When we went to vinyl 33⅓ rpm, the whole album could fit on one disc, but we kept the name) It was a pain keeping them organized, it felt like you were doing nothing but changing records and all the handling soon scratched the shellac beyond what purists could tolerate. Those purists have already got new re-masters of the best performers and artists of that era, without the scratches, and unlike vintage jazz, blues and folk, there really is no atmosphere added by hearing ancient surface noise with your Toscanini. If you do have old jazz and such, you may have indeed have something there is bigger market for, noise and all.
But if the packaging and contents are in good to fine or better condition, the sort of collector who values them as artifacts may want them, and there's always the chance there's a recording that everyone thought was lost forever. Or that was a niche market no one much cared about back then, like early Canadian music. That would be worth something, but the trick would be finding the expert to look at the trove and recognize it. If you think you might have something and can describe it to make it sound intriguing, I'd put the folks at the CBC Music Library, The UofT Faculty of Music and the Library of the Royal Conservatory of Music on your prospects list. Even if they haven't got money, they do have expertise, and maybe even a spare student who could come out and eyeball them. Check out http://www.78rpmrecord.com/ which includes selling tips.
