It is always nice to see when someone learns something they worked to find out. It's no simple task to find doubled dies, that's why they have value. Finding
Machine Doubling happens in nearly every roll, which is why they have no value.
You've found an example of what - for doubled dies - is a rather common die, but it is still FAR more scarce than
Machine Doubling no matter how you cut it.
Enjoy your coin - I am sure you earned the feather with a lot of hours of power searching...the fun way to earn them. As with any 'first', make sure you mark it as such and keep this one. One day you will probably be very glad you did. My first doubled die is in the hands of someone else now, and I wish I had it back.