If you google it, it says :
AI Overview
On a mouthpiece worked on or custom-made by Paul "Doc" Tenney, an "S" typically stands for a
"Slant" signature style or designates a specific, often
shorter, facing curve (similar to SMS) designed for a more focused, resistant, and vintage-oriented response.
Here is a breakdown of what the "S" means in the context of Tenney's work:
- Slant Signature Series: Tenney was famous for recreating the baffle and chamber of vintage "Slant Signature" Otto Link Tone Edge hard rubber mouthpieces. An "S" may be used to identify these custom-made, hand-finished reproductions.
- Shorter Facing (SMS): Doc Tenney often worked on Berg Larsen mouthpieces, which have "M" (Medium) and "SMS" (Short) facings. In some contexts, particularly with his custom work, "S" or "SMS" designates a shorter facing that favors a slightly more resistant feel, similar to vintage pieces, requiring a well-developed airstream.
- "S" for Specific Customization: Tenney was known for "blue-printing" mouthpieces, meaning he adjusted the table, tip, and rails to specific, optimized, and often unique, personal specifications.
Doc Tenney was a renowned refacer who took modern, harder rubber blanks and reshaped them to play like highly sought-after 1950s Florida-era mouthpieces, often leaving his signature "Slant" or "Tenney" mark on them.
Don't know if this helps.
I have said this before, when you have these problems you need to try before you buy,
If you go to some music shops and try mpcs you eliminate the ones that are not suitable, even if you don't want to buy new it gives you an idea what works and what doesn't.
You are just buying blind all the time and it's not working.