It'd be nice to know their motivation. Another person commented on the obvious possibilities: company went bust, they're too cheap to mail it, etc. But thinkin

It'd be nice to know their motivation. Another person commented on the obvious possibilities: company went bust, they're too cheap to mail it, etc. But thinking out of the box for a moment, are any of these scenarios possible? - Your prototypes were lost, stolen, or broken and they don't want to admit it? - It was taken by someone else (not stolen) and they can't get it back? For example, taken by a bank, investor, landlord, or government as collateral until a loan, investment, rent, or taxes are paid? - Does your prototype involve something like crypto (in certain countries) or weapons systems such that a government agency could have classified it or seized it? - Are they trying to exert leverage against you to do or not do something, but can't come right out and say it? That is, they want you to say it first?