When I mentioned the 50,60 and 70 series, I meant that it was discontinued and not used on 520, 620, and 720 series.  This emblem was embossed and stood out from the surface of the sheet metal. It was fragile and would break in half, if it was hit at all.  Shortly after they discontinued the 50, 60 and 70 series, the parts department was not furnishing this and was substituting a decal.  As far as 420s, they were made at Dubuque Works, and I am not sure just when they changed the paint color, to yellow and green. The 40s were all solid green.  We ran a tractor salvage yard for 25 years and the people that were restoring 2 cylinders, were always calling for that chrome emblem, which was no longer available, and they were trying to make the tractors as original as possible.  Below is a link that shows how the emblem was held on with two fasteners on the inside of the hood. 

https://partscatalog.deere.com/jdrc/sidebyside/equipment/77165/referrer/navigation/pgId/68382

http://www.tractordata.com/farm-tractors/000/0/3/38-john-deere-40-photos.html