Here's a late-use of the UX27D postal card by the Maine Central Railroad. The form on the reverse tells us that this (1916 vintage) card was pre-printed in 1923! You almost have to conclude that blank sheet stock of these cards was purchased and stored for many years prior to it's use.
This card is perhaps the rarest postal card of them all in mint condition. They're actually obtainable in used condition relatively easily (with $'s), but by no means are they common items.
Place mouse on image to see the reverse side of the card.