Having had a mis spent youth as an aircraft apprentice at Weybridge 1963 – 1968, it was my practice to grovel under bits of aeroplane under construction and pinch anything that had dropped onto the floor – amazing what you could find.

Amongst my finds were quite a few rivets, all colour coded. From what I remember, black was soft aluminium, mauve was a little harder and used for most joints, however there were self coloured and green rivets. These had to be annealed before use and had a 'short life' before they age hardened. So much so, that these rivets had to be drawn from stores in coloured pots, and each coloured pot had a life of about 6 hours. If you were caught using the wrong coloured pot outside of its 'life time' you could be dismissed. Does anyone know what the annealing / precipitation process could have been, as these 'hard' rivets tend to crack if set in the hard state. They were obviously an aluminium alloy of some sort

As an aside, all (dry) panel joints had a yellow anti scuff / corrosion treatment whereas wet (Fuel) panels had a short life Thyacol mastic applied – a devil to get off your clothes, but super for mending old car fuel tanks.