A beautiful 511/3 you have there Wayne. Nice video of the machine running. I own a 511/2 myself and my machine is still missing the original chimney. Your machine is listed in the Doll catalogs from 1929 and 1937. However, the production period can be further narrowed down if your machine still has a Doll sticker. If this sticker is green with red DC, then the production period is between 1929 and 1936/37. If the sticker is black with gold DC, then the production was between 1936/37 and 1939. An overview of all Doll machines can be found here:
http://www.fleischmann-toys.deHave a nice day