I don’t recall ever seeing that.
In any case, I never really trust square or rectangle tins. It’s not an ideal shape.
My mistake , they are vaccum sealed. But not design for long term storage. In my experience, not for short term either, or you need to tape the tin.
From another forum:
Rachel from Samuel Gawith checked in today on a forum, regarding the tendencies of some square tins popping open before a pipe smoker pulls them from the cellar:
“Every single tin leaving the factory is vacuumed sealed and then has a heat sealed anti-tamper strip put round it. Around 2 to 3 years ago the tin manufacturer we used suddenly stopped supplying through the usual channels so we had to find an alternative.
We did find a tin and tested it and all seemed fine. We ordered a container full as this is the minimum order and so there were thousands and thousands of tins received. Due to the design (3 little notches on the side) it meant that a good tight seal could not always be maintained over time. Therefore we went back to the drawing board and designed a whole new tin which has strips to catch the lid on all 4 sides.
It is very difficult to produce a square or rectangular tin that is perfect all the way around and so seals perfectly. It is much easier with round tins due to the way they are produced but round tins are more expensive to make and do not stack well for transport or on shelves in retailers.
And SG and GH have historically been in rectangular tins and so we want to stick with this. The new tin design seals well. It should not need a massive tug to get the lid off (then we get complaints the tins are too hard to open) and just because the lid comes off relatively easily does not mean it is not vacuumed sealed. BUT we do not design tins and make tobacco for long term storage.
This is a relatively new trend, mostly in the States.
We always advice anyone wanting to do this to store in a different container or vacuum pack the tins into bags. And in a humidity and temperature controlled environment.”
RachelSamuel Gawith & Company Ltd.