Please note that the key number of an Ahrend F key consists of a letter with 4 digits.
The number of the key can be found on the key itself or on the lock.
If it is not clear what brand of lock it is you can take a picture of the lock up close.
We need to see the entrance of the lock to be able to determine the brand.
The picture can be mailed to firstname.lastname@example.org or through WhatsApp to 06-20649337