Censoring money letters

[Sozont Singh]

Hello everyone.
My question may sound out of the strange or naive, but I'm curious about this :)
Was money letters censored? Yes, it seems obvious that no. But at the same time, if money letters do not pass the censorship, then after all, something forbidden can be hidden in them. Is there anything known about this? Maybe someone has met cover of a money letter with a censorship stamp?

[Howard Weinert]

Yes, all money letters from Russia sent abroad during WW1 were censored. Money letters could contain messages.

[Sozont Singh]

Howard, thank you very much for your answer!
It's even better than I expected! :)