Here are some distinctive styles of “POST CARD”. Otherwise, try my Publishers’ Initials Logos and Series page.
Carlo Bassani
Blum & Degen
Bosselman
Federal Engraving & Publishing Company
Louis Glaser
Golike & Wilburg
Alfred Holzmann
Knackstedt & Näther
K&N produced cards for a number of Scandinavian publishers in a distinctive font and wording.
Source: Famgus Vykort
Langsdorf
H C Leighton
Lichtenstern & Hariri
Modiano
The elaborate A in the first line of the address is perhaps more memorable than the postcard heading.
PB, Harlesden, London N.W.
Ritter & Kloeden
Rotary Photographic Company Ltd
The Rotograph Company, New York
Adolf Selige
Societa Editrice
Trenkler
Some of the cards issued by Ludwig Klement of Frankfurt (qv) also had this style, suggesting that Trenkler produced them.
Valentine & Sons
Wyndham & Company
Lawrence of Dublin used the same design albeit sometimes in green.
unknown American
possibly Blanchard Press
undivided-back postcards 