Interestingly, most designers/manufacturers used incorrect RIAA equations when designing, according to
Stanley P Lipshitz. Some were big names. I had a copy of his paper, which has been lost, but if memory serves me, some designs were off by some 5% or so.
Here is a link to an abstract, the paper can be obtain from AES for some $33.00/non members.
https://www.researchgate.net/publication/307925968_ON_RIAA_EQUALIZATION_NETWORKSI have used a 50.05 hz adjustment for decades in my test phono stage, but never got around to the treble side. I have tested using another break around 50khz, which makes an audible difference as well.
Cheers
steve