Be warned that some of them are huge. Sizes are in K (1024 bytes). If you choose a postscript file be sure you choose one that is suitable for your local paper size. Netscape uses <shift left-click> to download instead of view.
Here are some images of the GEC announcement of the KT88 from the December 1956 edition of Wireless World.
This is Mullard's announcement of the 'new' double triodes in October, 1953.
This is Brimar's advert for a 'new' range of miniature double triodes from February 1950.