You could use the 'Mark-recapture method' which is generally used to estimate fish populations, to get an idea of total numbers.
Basically for a given population (fish, or in this case Tintin Speedys), you catch several individuals and tag them (or make a note of the serial), and monitor the rate at which new catches are already tagged (already noted serial no) or not yet tagged (new serial no). You can then run this through an equation to give an estimate of the population size. Obviously accuracy is related to sample size.
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