The motif has seen a number of changes over the years. The first time we see the SPECTRE symbol is at a chess match in From Russia With Love (1963). The symbol is on a paper coaster delivered with a glass of water and a summons for Kronsteen, a chess grandmaster and SPECTRE agent. The symbol, with its four wavy tentacles and ghoulish head, is less an octopus than a jellyfish out for an evening's trick or treating. The device is seen again as an intaglio on a ring worn by Blofeld.
|From Russia With Love|
|Diamonds Are Forever|
|Spectre teaser poster|
|Spectre ring 2015|
There is one other comparison worth making. The Batman symbol has had a long history and has undergone many changes, far more than we have seen on the SPECTRE device. What is curious, though, is that the various designs of the SPECTRE symbol share certain traits with roughly contemporaneous Batman motifs. Thus, the octopus motif of Thunderball and You Only Live Twice has curved, enclosing sides, as does the bat motif used in Batman comics in 1964 and 1965. The thicker body and straight sides of the octopus in Diamonds Are Forever mirrors the thicker body and straighter sides of the bat motif that appeared in the 1966 TV series and in comics in 1970. The spidery lines seen in Spectre's 'bullet-hole' octopus recall the scored appearance of the bat motif used for The Dark Knight Rises in 2012. The official octopus symbol seen on the 2015 ring, meanwhile, has leaner qualities matched by bat motifs used in Batman Begins (2005) and later in comics, and itself has a vague appearance of a flying creature.
These similarities are no doubt coincidental, am I am not suggesting that the motifs resemble each other in any significant way. However, sharing certain traits, the motifs suggest a common aesthetic, the designers responding to an extent to the same influences or selection pressures within the cultural environment (although the apparent influence of Christopher Nolan's Batman films specifically on the Bond films has been noted elsewhere).
The SPECTRE symbol has seen a number of changes over the past 50 years, but remains a important and recognisable piece of Bondian iconography in popular culture and a potent symbol for James Bond's most tenacious adversary.
Note: The Batman logos are taken from an infographic published on the World of Superheroes website.