I'd love to get one of those early Rotaries - From what I've read, that is the earlier version - more often seen as Eldredge Rotary. Seems odd that a move from side tension to front tension would be a later version, but it appears so, and we know the front tension was pretty much standard with National Rotaries from later years.
Also very interesting that the decal set for the later front tension (like mine) is identical to that used on the side tension model - guess they had them left over and didn't want to toss them. Other than the change in the stitch length adjustor, they are very similar. The picture Needlebar has appears to be one earlier than in the link you shared, with the one in the link being more similar in shape to mine.