Abbreviation for “number” seen in inter-war architectural renderings

In my early years I have been fascinated why the word “number” is abbreviated “no” and not “nr”, which later I read in a book about printing fonts that the “no” shortening is a sort of tradition and was used as such since medieval times, when Latin was the most used written language, and comes from  “numero”, one of its Latin forms. I like the instances when the letter “o” is rendered sitting above an equal (“=”) sign or just a hyphen (“-“). The abbreviation containing the equal sign was often encountered in the inter-war period, adopted in many Art Deco designs, from famous posters of that era (adverts for transoceanic liner tickets, drinks, medicines, etc.) to architectural renderings like building or apartment numbers, etc.

I found during the architectural tour, which took place last Sunday, in Matei Basarab area of Bucharest, three cases of “no” abbreviation as architectural rendering, shown in the photographs of this post. The first one is the most attractive, with a catchy “=” sign under “o”, embellishing an Art Deco style house dating from the early 1930s.

The second image shows the name plate of a shop window blinds manufacturer, which most probably was active in the early 1920s, judging from the spelling of Bucharest (as “Bucuresci”) typicall for the period 1900s-1920s.

The third plate, seen in the photograph above, dates from the mid-1930s, indicating an workshop (perhaps a shoemaker or tailor) on the ground-floor of an Art Deco apartment block in the Jewish neighbourhood of the city (close by the State Jewish Theatre of Bucharest).