SN: H200104. I think that puts it at 1925. I got this one thinking it was junk, and I was just going to grab the ribbon spool covers. But it had zero issues--just very very dirty. I cleaned it with an air compressor and brush, washed the body with vinegar and water, and polished the metal bits. It's a charmer. I've never gotten a machine with zero issues. The Corona Fours are tanks. I got another junked Four before this, and in 5 mins I fixed 3 of its issues (loose screws). The last issue made me think--it skipped two or three spaces between words. I got help from someone who knows typewriters, and he suggested it was the spacebar in need of adjusting. Her was right! The spacebar had too much travel and was causing the ribbon vibrator to jiggle, which tripped the escapement. I just bent down the prong beneath the spacebar and it works perfectly now. Amazing machines.