~~~ notified bondholders after maturity, either... and many Series-E Bonds sat in safe deposit boxes (or under the kitchen sink ) for many years afterwards; dormant, and not making a penny. I know of one such case where pre-WWII E-Bonds were sitting dormant for over twenty years.

I'm also pretty sure that AT&T employees (during WWII) who bought both AT&T stock and US Saving Bonds, had each purchase matched by AT&T... and I think the AT&T program continued well after the war.