The replacement Bass drivers have been completed and are ready to fit.
I cleaned the alloy with some "T-Cut" colour restorer on a plastic scouring pad, the green bit, I pulled it off the yellow foam part, it was polished off with a soft cloth. I prefer the Black drivers to the natural, the colour is in the coating that was sprayed or brushed on by Celestion, its quite thick and rubbery, a bit like evo-stick contact cement when it has fully set. I didn't want to add any material and weight as the Bass unit contributes to the lower Mid Range and any additional coating would very probably ruin the output, so paint of any kind was out of the question. I decided to Dye the existing coating and did a test on the old driver to check for compatibility. I did this using two giant felt tip markers, the old permanent type of xylene marker that is Jet Black, none of this eco friendly Blue Black stuff that looks pants when you catch it in the light. I used the big 12mm chisel tip and quickly covered the cone. When the marker had dried, which only took a minute, I went over it with a lint free cloth moistened with some Isopropanol, this blends in any lines in the colour and gives a uniform finish. When the Iso had evaporated off I then applied a little Black Trim Wax to the cone and the rubber surround which was buffed off with a clean cloth. This gives a slight sheen to the finish and a little UV protection to the Marker colour. Again this adds nothing which will affect the acoustics. I did them one at a time and compared the sound of the cone between the one that was completed and the untouched one. When I scraped or tapped the cones they sounded the same so mission accomplished.  The old driver in the background has had some after market treatment applied which is about 0.5mm thick and has made the dustcap solid, this will have added a lot of weight and I think the sound would have suffered. It was fashionable at one time to paint these products on to paper cones, luckily the samples I found were original and only had Celestions treatment applied.