"Riveted action vs pivot action" ...British style concertinas - anglos, duets, englishes - historically have come with two common types of mechanism popularly called "rivet action" represented by the most common Wheatstone models and "pivot action" represented by the most common Lachenal models.Both terms indicating the method connecting the lever with the post.
The term "pivot action" is not very adequate since ALL are in real *pivot* mechanisms so I suggest "hook/saddle" types for the latter in stead despite there are in reality dozens of technical variants.

The main discussion mostly deals with comparisons between the major groups : 1) riveted Wheatstone-like and 2) hooked Lachenal-like but it may be added that late Wheatstones had 3) a saddle construction with a loose connection stabilized by an overfolded post

Anyway...When quality of different concertinas is discussed and compared this subject often comes up and arguments may be very determined regarding what model is the "best". My impression is that "riveted action" is promoted as a sign of "higher quality" but sometimes with vague arguments.

Therefore it would be interesting to hear opinions among players on this subject

Göran Rahm