@Dixie2011 there is "international notation" where the letters are replaced by numbers. So, 1. e4 is written as 1. 5254. Not very common though AFAIK.
This notation 5254 was common in international correspondence chess, to facilitate communication with people using different alphabets.
And - as far as I know - letter and postcards without written text e.g. just "stamps" were cheaper. ("Drucksache")
So you had a 4-digit "stamp" and saved money.
PS: Sorry, that's a bit hard to explain. Hope you got it.
