John Nickum wrote:

I guess that they must be very low energy beta particles, because if
they were able to penetrate the glass, they'd never have gone on the
market, even in the 70s.

So called "traser" key fobs and watches have tritium contained in
phosphor lined glass vial, the beta particles as you say don't make it
out unless you break the glass

http://www.glowrings.com/