I've got a set I picked up at a garage sale. One of these days I'm planning on putting up some pictures for comparison. They were non-disposable, which meant you washed them and the removable rubber seals eventually wore out. Since you were never sure when they were going to wear out, there were some extra precautions people could take.

That someone figured out how to create a new lid/ring system that was cheaper to produce, more effective, and worked with all the existing jars is a pretty impressive feat of industrial engineering.


[edit]

I just did some more research because I was curious. It seems some people used only paraffin for sealing. That method is now highly un-recommended.

For what it's worth, some people use washed out mayonnaise jars for canning. They don't stand up to the vacuum pressure good water bath canning produces, much less pressure canning. So "what people used to do" isn't always a good guide.