We have been using Acutex M310-IIE (Bilaterals) for over twenty years in our studios. It is an extremely rugged design, quite advanced for the late 70's. Works in all applications, unlike may Shure or other "open" needle designs such as Sonus, it withstands a lot of abuse. The extraordinary mechanical design of the 'M' series Acutex, provides extreme forgiveness from miss-handling from drops. The shield limits the vertical and horizontal excursions of the rotor from these types of accidents. It also provides a secondary EMI/RFI shielding around its rotor, making it extremely imune to those external noise sources. Very few, if any did that.
The Bi-Lateral diamond is cut to a .3mm-.7mm. pitch. Very close to an STR. Therefore, the tracking is quite excellent, as it sits deeper into the V.
Separation has been measured to be better that 35dB from 20-30kHz on our equipment.
Modern FFT Spectrum analysis shows it responds to the upper 60kHz range. This type of equipment or the newer RIAA test platters, were not available in late 70's era.
The published data sheet supplied shows it's upper range to be only 20kHz, while the STR model (M312-IIIE STR) had a published 45kHz upper range. In fact both performed well into the 50-60kHz range. Probably a marketing strategy, as the STR cut is very expensive to accomplish. It was called Spec-Manship, in those days.
Both the M310-IIE and the M312-III STR had identical bodys; tri-pole armature, and the rear induced magnet. Both stylus' are interchangeable with this model. They even work on the older M307 and up series, though the magnet was more powerful in the 310 and up series.
We have replaced these stylus many times over the years, alternating between the Bi-Lateral and STR cuts depending on the damage to the vinyl.
The STR cuts are 3.mm -.6 mm, making the STR a preferred mount into a damaged upper part of the V groove (clicks from horizontal damage).
All stylus are still available, though getting more expensive as time goes by.
Additionally, the stylus' can be aligned very easily from aging dried out dampeners.
A little twist, after soaking the rotor in alcohol overnight, does the trick.
Lastly, if your careful, you can tune out the +/- 2dB L/R channel to zero, by adjusting the armature to center over the poles. No cart designed made today can do that.
Overall, we have no problems in its use, or serviceability.
A real rugged workhorse, and outperforms many higher end units made today, which did not have the all the advanced shielding and built in safety features.
So, when your choosing a replacement for the V-15, consider everything.
Remember, the rotor, (aka: needle-armature), is the key to it's performance. The coils and method of MM (Moving Magnet, or Induced Magnet designs) differ only in its serviceability or repairability.
Warmest of regards,