These recordings have been well cleaned up, even if unavoidably at the expense of the highest frequencies. The sound recording level, though, is a little on the low side. The overall effect is impressive for recordings from the 1920s.
However, prospective purchasers may be in for a shock. This style of playing has now completely disappeared: nobody, anywhere, plays like this any more. As a result, these recordings make the pieces sound utterly different: different in phrasing, dynamics, and use of rubato and portamento; and, indeed, in the entire approach to these pieces.
This effect will sound weird to some people, but to others (maybe the older amongst us) it will be a glimpse of a vanished, forgotten world, where emotion and feeling (or, if you like, sentimentality) were at least as important as technique.