The early EWs went through a lot of design changes. It is quite possible they started out with the rear collector and silencer welded as a single unit, then went to a slip on silencer when the taxation weight restriction was raised from 200 to 224lbs (though I think this taxation change came into effect a few years later.) It might have been one of those items where they discovered it was made too light, and had to be changed to a more robust design. Likewise, numerous perpetually loose systems may have been 'repaired' by welding the rear collector into the silencer canister. Certainly from a replacement standpoint, a three piece system is far more practical and any two-piece systems if such were) would have eventually been replaced. Be aware if basing your conclusions on catalog illustrations, they are often retouched giving the impression of a welded system. Such is the case with the 600EW illustrations, where as in reality they were a three-piece system. These same catalog illustrations show the EW from 1926 and through 1929 on the cheaper models with the silencer body painted black.
Brake backing plates would originally be painted black, ditto brake arm.
Fork links would be nickel plate, the springs painted. Nuts on the forks are nickel plated, as was typically all small hardware.
Saddle springs (extension and leaf) painted.
-Doug
