[MarkMarine]

I am aware of those, but from what I understand the pre-80s ones are still better. I’m sure given a little time someone who is chemex expert will chime in and give a definitive comment.

[DougBTX]

Even if the manufacturing process is the same, pre-80s ones may be better on average due to survivorship bias: the weaker ones broke already.

[ngcc_hk]

Could they be different ent … use say lead … like some lens use radioactive material.