Not sure, the 4 looks to be smaller.

Lex

email (option): welbike@welbi**.net

I've enlarged and printed the picture, and measured the numbers. The 4 has the same height as the 5 and the 2. It's the 9 that is 10% taller... 🧐 Again something that is not really unusual with these old stamps.

email (option): wd.register@gmail.com