Hi Geoffrey
Welcome to the forum. You’re now the proud owner of a vintage AC and I'm sure you’ll be very happy with it.
I knew your car when in the ownership of Martin Quick who lived at the time in Gloucester (or was it Cheltenham?) I saw the car in the 1980’s and then again when Brooklands Motor Co was selling it a few years back. It’s in the same colour scheme now. I have a number of photos of your car – if you tell me your Email address I’ll forward them to you.
In answer to the questions you raise:
The S F Edge Special was a specific model. It was available during 1926 and 1927 only. It looked very similar to the Aceca model (like you have, but there were changes to this over the years) with longer wheelbase, different dashboard etc. Importantly, the S F Edge Special had more horsepower (56 and 66bhp offered, when 40 was standard). Options included high compression pistons, different ‘racing’ camshaft, balanced crank, three carbs. The name ‘S F Edge Special’ has since been misused on a number of vintage AC’s.
Three carbs have been fitted to a number of vintage Sixes, and was a factory option for retrofitting during the late 20’s and later. Coil ignition was on some models in 1928, all models 1929.
You say you intend to look at the back axle. Does it have problems and what are they? You ask about gear ratios. Standard, on your 1929 model, were 5:1 (top), 7.9:1 (2nd) and 14.7:1 (1st) though the factory did offer alternatives at an extra charge of £10!
As far as I know a water temp gauge was not fitted to the dashboard in production (though it was on the Magna model) An article in The Motor 1928 showed work on thermostats, cable brakes, brake compensator etc but likely these went by the wayside due to the company's financial situation.
You should find a spare wheel, as these Rubery were not specific to AC, but where has the one from the car gone? It was with it only a few years back. The timing chain is an inverted tooth and over the years they stretch. They can be restored, tiresome riveting involved, but it can be done. One vintage owner had three on the shelf when I last saw him. When vintage engines are being restored an option then is to convert from inverted tooth to a duplex chain. Which do you now have? Both are available, but the inverted is now difficult to find and likely a ‘restored’ one would certainly do. Some owners who have converted the sprocket and chain still have the original type.