p 50 of the Tiger-Fibel shows how "swiping right" worked in the 1930s, with an upper right corner drawing of the table telephones from the "Femina Palast" Berli

p 50 of the Tiger-Fibel shows how "swiping right" worked in the 1930s, with an upper right corner drawing of the table telephones from the "Femina Palast" Berlin nightclub. https://archive.org/details/Der-Generalinspekteur-der-Panzertruppen-Die-Tiger-Fibel/page/n47/mode/1up https://archive.org/details/Der-Generalinspekteur-der-Panzer... (it's in the radio/intercomm section, so it looks like tech manuals going ahead and duzing the reader are nothing new?)