The "Horror Monster" mask by Topstone that became "Shock Monster" is one of the indelible icons of the Monster Craze that swept America in the 1960's. It's hideous trademark visage, instantly recognizable by the mop of electrified hair, decayed skin, and popped-out eyeball, looks like someone got their head run over by a truck and was buried without the benefit of a mortician's craft and exhumed a few years later.
The Shock Monster mask gained its greatest notoriety from it's ubiquitous advertising in FAMOUS MONSTERS OF FILMLAND magazine. Thousands of kids saw this and other spooky Halloween masks for sale all year long, and I'm sure hundreds, if not thousands, ordered them through FM's mail order department, Captain Company.
Here are a few examples of the Shock Monster as it has evolved over the years. Images can be viewed all over the web, from sources such as eBay, TUMBLR, the Halloween Mask Association and the Universal Monster Army.