Emeco 1006 Chair 1944 vs 2012  

Hi,
I had some questions. I'm very curious about how the chair has changed. This has clearly happened because brand new ones now have big stamped "EMECO" on them.
I have a set of 1946 Goodform (General Fireproofing) Navy chair which is lacquered and brazed together with an under seat damper (stamped 7/46). Additional differences to a modern chairs is that it has less aggressive bends in the horizontal support bars and round rubber fittings attaching the gliders. It also has a bolt connecting the back to the seat. (The bolt, lacquer, and rubber fittings are very similar to an upholstered EMECO I saw from 1960.)
I also have set of 80's-90's vintage EMECO chairs which have awful weld jobs which are not ground flat like the new ones. I think these are powder coated. They have "EMECO" and "EMECO/METWOOD" gold tags and no stamped markings.
Short of telling me to cantact EMECO, my questions were:
Were Goodforms just close but not exact copies of the Emecos hence the small differences in design? Were very early Emecos also brazed instead of welded (MIG welding just being commercialized in 1944)?