What years were B&W 803 series 1 manufacured?

Would also like to know what the differences are btw original 803s and the series 2!
The changes in the M803-S2 were in the construction of the internal Matrix cabinet I believe. The original M803 did not sound that much better than the M804, so it did not sell well (cost 50% more).
According to Orion Blue Book:

M803 90-93
M803 S2 94