I added a couple new words to my own vocabulary when I came across this article about a coin and currency expo in Tiruchi, India. -Editor

OK, I know what a palindrome is - a word, phrase or number that reads the same way forwards and backwards, as with the word "radar". Banknotes with palindromic serial numbers are often called "radar notes." But what are ambigrams and strobogrammatics? Read on. -Editor

"A strobogrammatic number is a number whose numeral is rotationally symmetric, so that it appears the same when rotated 180 degrees. In other words, the numeral looks the same right-side up and upside down (e.g., 69, 96, 1001)."

"An ambigram is a calligraphic composition of glyphs (letters, numbers, symbols or other shapes) that can yield different meanings depending on the orientation of observation. Most ambigrams are visual palindromes that rely on some kind of symmetry, and they can often be interpreted as visual puns. The term was coined by Douglas Hofstadter in 1983–1984.

"Ambigrams can be constructed in various languages and alphabets, and the notion often extends to numbers and other symbols. It is a recent interdisciplinary concept, combining art, literature, mathematics, cognition, and optical illusions."

Above is an image of a radar note. Who can provide images of banknotes with ambigramic or strobogrammatic numbers? -Editor