I don’t think there’s much to debate.
Out of the small handfuls of original as found bikes of either year, 37/38RMS.
Not one had been found with an originally applied Master Weld decal.
The few 37’s to date have the winged CWC decal on the fender, but not all the originals have this feature.
Of the ones that do, some are high on the fender, and some are low on the fender.
The 38 literature makes a strong statement, that all of the Roadmaster line has a frame that is 100% stronger, and to be sure to look for the Master Weld decal on the seat mast/tube.
It makes sense, that they would want the decal on the frame, since that is the part in question, and that it is the one part of the bicycle that’s not going anywhere during its lifetime.
Are the 38 Roadmaster Supreme’s considered to be part of the Roadmaster line in 1938?
It sure seems like they would be.
Especially since they were the flagship models for that year.
When I had the frame stripped, it definitely showed fillet brazing for cosmetic purposes, but those were not enough to hold the frame together.
I can’t say for certain that the 38 RMS’s were constructed using the new Master Weld technique, but I suspect that they may have been in part, with some brazing for cosmetic reasons.
The safe bet, was to leave the decal off, and that’s what I would recommend, but in my case, I wanted to use it, mainly because the company was so proud of it, it looks so cool, and it was such a defining feature of the 1938 Roadmaster model year.
And for fantasy sake, if you were going to use it on a 1938 Roadmaster Supreme, the literature clearly states, to look for that symbol on the seat tube.
That’s my two cents.