post-office order n. now rare a money order for a specified sum issued upon payment at one post office, and payable at another (named) post office to the person specified in a letter of advice.

[OED]

post-office order, noun

Definition of post-office order

British

: a money order issued by a post office but not bearing the name of the payee which is given on an accompanying letter of advice

[M-W]

"post-office order"---first documented use 1815 [OED]

Links zu den Zitaten in #2 :

https://www.lexico.com/definition/post-office...

https://www.merriam-webster.com/dictionary/po...

... dazu auch :

https://www.encyclopedia.com/humanities/dicti...

 POO

... Post Office order

The Oxford Dictionary of Abbreviations ...

postal order n. a form of money order issued by a post office for the payment of a specified sum to a named payee at any post office; (formerly) such an order for one of a number of fixed sums.

P.S. @#2: ; in my day I was familiar only with the "postal order" [first documented use 1864], also apparently used in the US; OED glosses them slightly differently, but they seem to be much the same thing; Dictionary: postal order

In Deutschland gab es die Postanweisung - wobei da der Geldbriefträger das Geld ins Haus brachte.