We found a Dutch Lucky Strike ad from 1932, in which the use of "modern Ultra Violet Rays" in the toasting process was specifically mentioned (the highlighting of the word in the picture below is done by me) and the words "Ultra Violette Stralen" were given a very prominent place in the text, thereby focusing on the modern scientific nature of the process.
Another 'unique selling point' for this ad is explained in the heading "Versch uit Amerika", which translates to "Fresh from America". In Dutch too, "vers" (versch is old spelling) has the double meaning of "not stale" and "new".
Interestingly, in the American version(s) of the ad campaign, the word modern does NOT appear, instead, the focus is on the analogy with the sun:
"Everyone knows that sunshine mellows, that's why the 'TOASTING' process includes the use of the Ultra Violet Rays"
|Lucky Strike, Haagsche Courant, Jan 23, 1932|
Examples of the American ad campaign can easily be found on Google by searching "Lucky Strike Sunshine Mellows ad campaign".