Lettercard

That it is folded over gives the writer twice as much room for the message compared with a postal card.

The message is written on the inside and the card is then folded and sealed around the edges.

The recipient tears off and discards the perforated selvages to open the card.

The lettercard was first conceived by a Hungarian named Akin Karoly[1] and introduced in Belgium in 1882.

[1] As with adhesive stamps, a perforation gauge will be a useful tool of the trade.

1892 imprinted 1d letter card uprated with 1d and 1/2d postage stamps sent from London to Germany, complete with selvages
1943 use of an early aerogramme inscribed Air Mail Letter Card . That it has an adhesive stamp , rather than a prepaid imprinted stamp or indicium , means that it is not postal stationery. Instead, it is a formular air letter card.