For those who wish to speculate further on the meaning of the Saturn symbol, this is what I have discovered so far.  We know that the symbol represents Saturn, which is a great start.  The symbol is often analysed in three parts, and it may also be useful to reference a table of typical astrological signs (these do vary a little depending on their source).

This is the astronomical symbol for Capricorn, the goat.  The Zoso symbol is for the planet Saturn, and at the front or head we have the symbol for Capricorn.  Saturn is the ruling planet for Capricorn.

 This one is much more interesting.  The circle with a dot in the centre could be the sun (also an alchemical symbol for gold), and the axis and “S” representing the rotation of Saturn round the sun and Saturn’s role in resolving karma (the grim reaper).  In astrology, Saturn alternately brings fortune and pain – a cycle, perhaps linked to the rotation of Saturn round the sun (which it does once every 29.45 years).  Another similarity is to one of the alchemical symbols for Mercury (this picture taken from Fred Gettings dictionary of alchemical symbols.  The association here with Saturn is that Saturn’s rings gives the planet an appearance of constantly changing, as Mercury is a liquid at room temperature constantly changes shape when swirled around in a flask.  Astrologically, Mercury people are said to be cautious, methodical, and a hard worker (which would be a great fit for Jimmy Page), but I am not entirely convinced that the Zoso symbol represents Mercury in Capricorn.  I prefer the linkage to rotation around the sun.

This final part of the symbol has puzzled many people, and despite a lot of searching there isn’t really anything similar to it.  It could be an embellishment intended to show a support (for the 0-S-o element above).  There is an alchemical image for Cancer (again, I got this from Fred Gettings’ dictionary), which is Jimmy Page’s moon sign, but why should the symbol for Saturn also have the Cancer symbol in  it?  This may simply be an artistic extension of the “Z” Capricorn symbol, but the alchemists usually built meaning in to everything they did.  Of the three parts, this one remains a mystery.

The similarities to the signature of John Tenniel has been noted.  His signature is a styled J and T.  Have a look for yourself.