How are you playing your precious MONO Vinyl?

@elliottbnewcombjr How would using a stereo cartridge on a mono record damage the record? I can see that using a mono cartridge with no vertical compliance (eg Miyajima) on a stereo record could cause a problem, which is one further reason why I converted the Ruby 3: it retains it's vertical compliance but produces no signal from such movements.

As for the Beatles, I have my brother's original Parlophone mono releases, and have only ever played them with RIAA equalisation. I don't know if they were recorded that way, but they do sound fine.

I had Steve Leung of VAS convert an older BM Ruby 3 stereo cartridge by rotating the former holding the coils 45° and connecting the horizontally sensitive coil to both outputs. He removed the disconnected coil and put a new stylus on it. This was a lot cheaper than buying a new mono cartridge. But back to the original question:

Is EQ-100 or something similar, absolute necessary from a purist perspective or should I take the pragmatic path and use the ‘Mono’ switch on my Integrated with a built in phono?

If you have a true mono cartridge there is no need to use the mono switch on your integrated amp: each channel is receiving exactly the same signal, so it should make no difference. As to whether there is an advantage to using a mono phono stage, that is a matter of the relative quality of the phono stage you use now versus the proposed mono stage, but I don't think there is a reason to say that a mono phono stage is always better than a stereo stage used with a mono cartridge. If a purist approach is to be taken, with a mono amplifier and a single speaker, it would conform, but that involves a whole separate system and I don't think that's your intention.

@billstevenson If what Ortofon told you is true, then all of us who can hear a difference between a true mono cartridge and the mono button must be mistaken, which seems unlikely.

I spent a long time examining the description they give of the Cadenza Mono (which used the same wording at that time as for stereo Cadenza cartridges, and added the term "dual coil mono") and ended up buying one. It doesn't get used—I'll happily sell it—as it doesn't sound anything like as nice as the Ruby 3 I had converted to mono (coil assembly rotated 45° and the laterally sensitive coil connected to both sets of pins).