Let me run this by you. I think it's safe to say that since the RS1i came out in 2009, my n.o.s. RS1 must date back to around 2008. this would mean that Grado would have manufactured about 18 000 RS1 in the last 7 years or so. this would add up to 2600 pairs a year. Now, depending on how many working days, Grado's employes averages, I think it's safe to assume that Grado would have had to make roughly 8 to 10 pairs of RS1 a day. I'm no expert, but this seems to be in the realm of possibilitys.
That felt like I was back in school again, solving maths propblems.
The quadratic equation and permutation theory is indeed correct.