I'm browsing around in Chinatown yesterday checking the Vietnamese packaging for the Sen and Lai characters. Its a mixed bag of characters with or without the grass radical. There are plenty of large pretty boxes of various teas in the 300g range which makes the tea more expensive which I usually ignore. I found a brand from Taiwan called SunLong. It was discounted at one of the tourist stores and you can't go wrong with tea from Taiwan except for my last and only batch of Oriental Beauty. There is a thumb press on the large round lid which has to be pressed to slide on and off. It can't be forced otherwise. It took awhile to figure out the patent principle. The thumb press seats a small rubber seal which allows air to rush out when capping and in when decapping. There isn't enough clearance between the lid and container for the air to escape otherwise. I've talked about the partial vacuum created by volume displacement from a lid in other posts. The green tea comes in a nitrogen pack which I'll break one of these days. The packaging is hard thin brittle plastic which I don't think would cause a problem even in hot climates.
Jim