How are you playing your precious MONO Vinyl?

I don't have any phono stages with options for the de-emphasis curve.  They are all RIAA.  And since this one pair of LPs on EMI are the only LPs where I have ever noticed a possible problem, it has not and will not be worth my while to buy one.  I have several other copies of Louis and Ella both original pressings and re-issues that sound fine with RIAA.  I would wager those EMI pressings are original in the UK, because the LPs are obviously very old; the quality even of the album cover jackets is sky high. If I ever have access to a phono with options for EQ, I will give them a try.  when I was a kid, my parents had a Harmon Kardon mono receiver which did provide at least 3 curves.  I used to play with them while listening.

⬆️ It makes sense not to chase a specialized phono stage for just one anomaly, especially when the rest of your collection sounds great through RIAA. 

Thanks for your participation! 

If you look at graphs of the various curves generated by the different algorithms, they are not terribly different from one another, because after all the goal was essentially the same.  So I might be happily listening to some of my 50s mono LPs where the pre-emphasis was other than RIAA via the RIAA de-emphasis curve built into all my phono stages; I just don't hear a problem, except maybe with those Louis and Ella recordings on EMI, which date from 55 or earlier.

Here’s a question. Suppose you have a mono cartridge but don’t know whether it’s a true mono or a bridged stereo type. How would you tell the difference?

I asked essentially this same question a few years ago to the experts at Ortofon and the answer is there is no difference electrically and, therefore, no difference sonically.