
It looks like this full-page ad ran various times in different publications from the late 1949 to mid 1950.
Palomar Skies a blog with news and information about the Palomar Observatory. Postings here will cover current research, history and public outreach events taking place at the observatory.

Click to embiggen and you'll be able to read the text of the ad. The photo shows the honeycombed back side of the 200-inch disc. Standing with it is Dr. George V. McCauley (left) and Dr. J. C. Hostetter. Dr. McCauley directed the project of the casting the huge Pyrex disc.
Kodak produced the photographic plates that were used at Palomar for years. The last photographic plate shot with the Hale Telescope was taken in 1989. We continued to use Kodak plates for the Second Palomar Observatory Sky Survey, performed with the 48-inch Schmidt (aka the Samuel Oschin Telescope) all the way up to the year 2000.
This was not an "official" ad in that it (thankfully) did not mention Palomar Observatory by name. There have been many ads that have done so. From time to time I'll be posting a few of them here.