Mine was always 4011... closely followed by 4001, 4020 and 4017.

@Extelec I once owned about 10,000 4020s that I'd bought from Bonex for £50, which also meant that I'd cycled the 11 miles home with them on a bike without panniers. It took me years to get rid of them at rallies and still find tubes of them in unexpected places. I still remember the huge box that they were originally in had a hole in it and it would occasionally launch some tubes of 4020s as I cycled home.

@Extelec thinking about it, it must've been more like 2,000, an unmanageable quantity …anyway