I was thinking about letter boxes and thus about the size of envelopes. My sister lives in a short but steep late-Victorian street. All the houses are very similar (apart from the one on the corner) and they've all retained their original front doors. But hers seems to be the only one with an original late-Victorian letter box. Shiny (or would be if she polished it) brass, with LETTERS cast into its flap in attractive capital, er, letters, in case late-Victorian posties were confused. But it's too small to get any modern post through! Every year, she displays a row of concave and convex Christmas cards.