Mono Reissues and the Conical Stylus

Dave, You wrote, "My take is that if the coils remain oriented at a 45º angle to the record and then wired in series for mono then it is a stereo cartridge wired for mono and it doesn't matter if it if done internally or externally. If however the same parts are used for a mono cartridge and the coil is oriented so there is only pickup in the lateral plane, then it is a mono cartridge. In this case there would be only be windings for pickup in the lateral plane and the windings at 90º to that plane would not be used / wound."
That is also what I and many others have been saying here and elsewhere.  What I wondered about is whether from a purist standpoint, does the true mono cartridge offer us a level of performance in the mono mode that cannot be had via the bridged stereo approach?  I guess that if you use bridging, then cancellation would be imperfect to the degree that the two channels of the cartridge are not perfectly matched, which probably never happens.

Goofyfoot,
the groove width of the London ffrr is about 2.5 mil which is above the max spec for microgroove. Since the groove is v shaped the width has little to do with whether a conical will properly trace it.   the only issue that can arise is a 1 mil conical can disengage from a microgroove but a 0.7mil conical will not run into any more issues with a 3.2mil groove than it will with a 2.2mil microgroove.  In fact a 0.7 mil playing records previously played with a 1 mil will often be much quieter since it traces a part of the groove that hasn’t been played.  

Just measured a bit closer and the groove with is closer to 3 mil.  I should also clarify that the 2.2 and 3.2 mil numbers I gave are the "average" from the link below and not a hard spec.

https://dgmono.com/2018/04/06/deep-groove-mono-and-the-great-groove-width-mystery/

Dave, here are a couple of sources which explain different styli and groove dimensions as well as other things.

https://www.badenhausen.com/VSR_History.htm

https://dgmono.com/2017/02/17/modern-mono-playback/

I think we're loosing site of what matters, being what stylus type would work well between older mono pressings and newer mono pressings? The reason why I believe this is in need of discussion is because stylus geometry changed with the evolution of the record. I don' think anyone would disagree that the 1 mil. conical stylus, while optimal for early mono records, wasn't ideal for later stereo records. 

I understand that early mono styli track well and sound fine riding higher in the groove than a stereo styli needs to (i.e. pinch effect) however this is not he only reason for considering what differences between styli are important.

Here is a nice article on the subject.  https://dgmono.com/2018/04/06/deep-groove-mono-and-the-great-groove-width-mystery/
It is the stylus radius that is the most important measurement not the shape of the stylus. The smaller stereo stylus might theoretically pick up more noise from trash at the bottom of the groove but if you have clean records what does it matter? Older Mono record from before 1962 and re releases made from the same masters have a slightly wider groove. The shape of the groove is exactly the same 90 degree V with a very small radius at the bottom. 
If you are wealthy and can buy cartridges indiscriminately, wonderful. I am not. I would rather spend my money on one great cartridge than two not so great cartridges. I have quite a few mono records and I never switch cartridges to listen to them. Might they sound better with a conical stylus and a mono specific coil layout. I do not know as I have never been able to make that comparison. I do know that a modern stylus has significantly less mass than a large conical stylus. Consequently all other factors being equal the modern stylus will track better and cause less record wear.