Not sure why you didn't get a reply to this...

The plates are fast negative emulsions for making prints. Because they are (were) quite fast by the standards of the day (maybe 1950s), they will almost certainly have figged to the point of being useless. So, if the packets are in nice condition, keep them as collectible curios. If they are scruffy, you could try a couple to see if they give any sort of image. They are known as quarter plate, so you'll need a quarter plate camera and they're panchromatic, so only open in complete darkness. If you haven't got / don't want to get a quarter plate camera, you could just chuck 'em back on ebay. They are unlikely to fetch much (99p!) but some people buy them for the packaging (collectors) and some buy them for the glass (they can be cleaned and coated with home made emulsions, or used in printing frames etc.) Some can't resist the temptation to try them out to see if they can still get something