Love them, so nice!The 'per luchtpost' (= via air mail) / par avion) label must be a Dutch one (not Belgian, as the PTT used to be the Dutch mail (= Post; and Telephone and Telegraph) company).
I received it on a letter form the United Kingdom. Not always people use the official labels from their countries... I've used Australian labels on my letters, for instance :-)
I love those labels....and somehow recognize my handwritting ;-)
Thank you for coming. All your comments make me extremely happy.