I now have a dewar flask that will hold the plastic. However, it's an open, large mouth type and not something I can fill at the LN2 store. Still looking for a safe way to get LN2 home without buying a transit dewar.

For those curious about this conversation, I'm attempting to free a metal token I got from Jim in a lucite block. Home freezer, then dry ice followed by a big hammer did not work, although I can now see separation of the token from the solid plastic. I think about -200 degrees C will do it and liquid nitrogen is probably the mechanism.

Stay tuned .