I'm not into bitcoins nor physical wallets, but I'm guessing those are not supposed to attach any gsm network ever.
Isn't that trivial to detect, even without opening a device, that something inside is attaching the gsm network? Those are pretty strong signals in a well defined tiny range of frequency, after all.
(Not so long ago you could hear them talk with the towers through regular home speakers.)
(Not so long ago you could hear them talk with the towers through regular home speakers.)