〆 is a shorthand symbol for shime, which can mean like 'end, conclusion, resolution' on its own (you can also see it in words like 〆切り 'deadline' and so on). Not sure if that helps understand what it means as a tea name, though.
Note to the translators - seehen yaro isn't standard sore hen darou, it's shinai darou. (If y'all ever need help with nonstandard Japanese, feel free to hit me up!)
Otherwise, a wonderful chapter (^^)
Pickled vegetables are a huge part of Japanese food, but I don't know how many are ready-sold versus just made at home. I wouldn't be surprised if they're sold in some other packaging, too.