I would like to see what a multibillion dollar bond looks like, hee hee. Maybe they can sell it on ebay once the IOU is cashed in.
The only reason they are in a file cabinet in physical form iirc, is because somebody kept inquiring “where” the bonds were.
I don’t know much about treasury securities, but these are “special” bonds, as in they are not marketable treasury securities. I’m not sure if that’s good or bad from the standpoint of America. Probably bad. If they aren’t marketable, then they can be more characterized as an IOU, since they can’t be sold afaik.
The “lockbox” was un-locked in 1968, in order to make the budget look good after billions in social spending and defense spending because of the cold war/Vietnam War. So all the tax income came in to the general fund rather than kept in a social security pool.