In my experience....they just come out...no prying necessary...not attached in any way....
Turn the lid upside and rap sharply on the counter....the milk glass insert should fall out.
Linda C

I'm curious, are you doing something with the glass? Making something?

I'll bet she's going to paint them and stand them on a little easel and sell them!
Linda C

Well, I tried to figure a removal method and have concluded that the zinc cap is formed around the glass insert when it is made. The glass part seems to be under a ridge around the entire cap. Soooo- I took some big bolt cutters and cut diag cuts around the sides of the cap.7-8 cuts. Bent the pieces out like flower petals. Carefully--used a hammer and flattened the petal part near the glass as flat as I could. Then used a small screwdriver and gently pried under the glass in many places around the glass. Popped out. 3 out of 5 came out successfully. 2 broke into many SHARP slivers. Labor intensive. Haven't given any thought to how to use them.If ya try this--Use gloves! If anyone has an easier way, please post it.
Thanks, fredda

I would think that the old zinc alloy canning lids would be collector's items by now. If you have what I think you have, its the type that used a rubber ring to seal the cap to the jar. The rubber ring had a pull tab to make it easier to pull the ring out when you wanted to open a jar. I haven't seen those things in ages. The popular item today is rings with lids with a slight dome. When a good seal is made and a vaccuum form on cooling, the lids snap down. Lids tht stay up indicate a bad seal.

The zinc lids didn't take the rubber rung with the pull tab....that was the jars with the glass cap and the wire. The zinc jars took a plain ring with no tab.

Just call me lazy, but, I would have have to have an idea of what I wanted to do with them before going to all the trouble of removing the rings like that. Not to mention the danger involved in getting them out. IMO safety glasses are in order as well as gloves.

My mother canned, but I don't remember this type of canning lid. Does anyone have any info as to how old they might be and if there could be any collectibles value to them?

Very interesting thread.

You could dissolve the zinc in acid, but it's just as risky as broken glass, unless you REALLY know what you're doing! Would have to be done outdoors for certain.

Those lids were used from maybe 1870 to about 1930....pretty much guessing here based the ages of jars I have seen.
And yes they have collectors value....not a lot but some. Broken with the glass removed and the lids cut up...almost no value unless you find a crafter who has some clever ideas.
Linda C

They sell for $1.00 on up at the antique malls.
Millie