This is the old pre- 1955 logo of British intelligence/Mi5. A brief sketch follows:
The overriding symbolism is occult and represents the "Eye in the Triangle" that can also be seen on the back of US banknotes. In other words the "all seeing eye" of the Egyptian god Horus.
There are also a lot of Rosicrucian echoes involved in this too. This derives from the fact that the Rosicrucian order was founded by Sir Francis Bacon and that he, his brother (sons of Queen Elizabeth - the 'virgin' Queen) and others in his circle were "inteligencers".
This was at a time when Bacon and his circle had two aims. Because he was of royal blood he was fighting for science over dogmatic religion -- hence the founding of the so-called "invisible college" that we know today as the Royal Society (see:
http://royalsociety.org/page.asp?id=2176 ).
The second aim was to defeat the machinations of the Vatican - hence the informal intelligencer role he and others adopted - that continued to attack his mother's person and throne by overthrowing the Tudors and their creature, the Church of England, thus returning the British Isles to Catholic diktat.
It ia interesting to note that one of Bacon's friend and teachers, the occultist Dr Jonathan Dee was the origin of Ian Fleming's spy character James Bond - 007. Below is an image of Dee's signature which had as its symbolism his two eyes beneath the number '7' that as a special significance in occult and cabalistic circles and also had the meaning of "For Her Majesty's Eyes Only" (see:
http://www.sirbacon.org/links/dblohseven.html)
The MI6 logo today looks like this:
And still has echoes of its Tudor past in the five-petalled "dog rose" of Tudor times - but combined with the Portcullis Gate to signify that the kingdom is a parliamentary democracy (allegedly anyway).