Pure snobbery to dismiss the M4-2 as not real... even if Leica did not make it up to the standard of the M4.
The M4-2 represented a big change for Leica with respect to the manufacturing process. The M3, M2, M4, and M5 manufacturing was much more individual bench craft with a huge amount of hand labor associated. The costs of such manufacturing were skyrocketing over the decade between 1965 and 1975 such that, coupled with other unfortunate developments (poor sales of the M5 and very high warranty costs with the CL, plus the costs of developing the R system line), Leica was in a profitability crisis.
The M4-2 was an M4 that was simplified through the refactoring and redesign of subassemblies into larger component assemblies in order to enable a more efficient, less hand labor intensive manufacturing process. For instance, (at least from what I've been told) the viewfinder assembly process went from the hand fittings of 25+ parts in 20+ operations to fitting 4 parts in 5 operations on the production line. (If not an absolutely exact correlation, the scale*of the change is about right.) The viewfinder components themselves were simplified, redesigned to be machine-assembled to tolerances that matched the previous hand assembled and fitted methodology.
Is this "not making it up to the standard of the M4"? Or is it really making the camera in a wholly different way? The change is really the movement from a old-school, 'one at a time' craftsman methodology to a modern, more batch-oriented manufacturing methodology. The standards of precision, build quality, and robustness are pretty much the same with a carefully engineered and designed product, but the costs are hugely different.
The transition to this more efficient, economical manufacturing methodology enabled Leica to return to profitability and stay in business. The M4-2 being the first M camera to be manufactured in this manner makes it unsurprising that the early examples of the first production run might have had some build issues, all of which were corrected as Leica gained expertise in the new manufacturing process (and most of those cameras still extant with original production defects have long since been updated and the defects corrected at this point in time).
In a sense, the M4-2 is the M that saved Leica from extinction because it was the model that proofed the viability of the new manufacturing methodology and gave hope to restored profitability.
As I said before, this is old ground that countless threads have covered before. My M4-2 is every much a delightful, robust, beautifully made Leica M as my M3, M2, and M6TTL were, and as my current production M-P is. The M4-2 is always a pleasure to take out and make photographs with, just like the M-P, and that's what counts.
🙂