MSP - You DO HAVE one of the 1st Model 1st Variations - most likely made in 1931 before the 1932 catalogue hit the shelves. These earliest pieces have fixed/non-adjustable half circle front sights, windage adjustable rear sights, round finger grips on the barrel latch, "key-hole" barrels, cylinder release bar on right side of quill, one-piece wooden grip and nine-shot cylinders (if your's is a 7 shot, please provide the cartridge stamping on the right side of the barrel). I have s/n 604 with all those attributes. I also have s/n 1431 which is also a 1st M, 1st Var. but by that s/n the front sights had been made height adjustable with an elevation screw through the front of the rib. I would really apprciate having the full serial number of your piece for research. The lowest previous s/n I've seen was in the mid 200's.
As for low serial numbers, I have a 1st Model 1st Variation American Double Action with s/n 14 - it is in mint condition.
p.s. Knight Model 999 s/n B50xx was made in 1941.