My 99K was built in Scotland in 1950 but it looks like a 99-13. It has no stitch length regulator. What's up with that? How come the manual for the 99's and the 99K's shows a stitch regulator? The serial number is EG038445. I'm confused, apparently it's called the "older series". So I guess I should be looking for stuff on the 99-13 then huh?