About how many Valentines were posted one year after Britain's Penny Black was introduced? About 400,000 were sent by post.
The Penny Black, introduced in Britain in 1840, was the world's first adhesive postage stamp. It accompanied postal reforms associated with Rowland Hill, which sharply reduced the cost and complexity of sending letters. That made Valentine messages affordable to a much wider public.
Before the reform, postage was expensive enough to restrict ordinary correspondence. Afterward, people could mail cards more easily and anonymously, helping Valentine's Day shift from a private exchange toward a mass commercial tradition. The figure refers to Valentines posted in the United Kingdom, not the number produced worldwide.
A nearby milestone is that about 60,000 Valentine cards were sent in Britain in 1835, before the Penny Black. The later total therefore represents a dramatic rise, not a modern annual count.