Hi !
There were two kinds of yellow labeled Fiamme rims. In the fifties the label was oval and showed a helmet of a knight with the words "BREVETTO LONGHI" and "CERCHIO FIAMME" around it. The normal rims had a red label and the label of the extra light was yellow.
In the seventies the label was rectangular and the yellow coloured label was placed on the Fiamme Ergal - rims.
I found such rims on a bike from 1977. Here in Austria these rims are very rare, because they are VERY light and dont' live long.
Greetings from Vienna, Austria
Werner Schuster