Y/T Numbers For 1968 Telegraph Stamps?

Hi!
Just joined for a little help with a few things. Last year my 86 year old father showed me his album from his youth in Schwyz and I endeavored to finish his album as best I could. I ended up going crazy and nearly filled two Lindners (Cantonals to 1959, except the first two pages) of mostly Mint stamps. I still need to fill in the holes in my dad's album, but it will be much more of a process than with Lindner pages.
Anyway, my question is, could someone clarify the Y/T numbering for the 1868 stamps and 3fr 1874. I know 1877 are the B (1-6, no 20 fr) and 1881 (granite paper) are A (1-8, no 7 (was for gold gilt 1868 as 7B).
Thanks in advance to whomever can clarify this for me.
Cheers
Ruckus

I'd suggest moving to Michel (arguably the go-to for anywhere in continental Europe) or Zumstein (the specialist bible for Swiss philately) and saving yourself the Y&T aggravation.

I'm using Zumstein and SBK, but some places I'm looking only list Y/T.

Yes, Y&T lists more telegraph stamps than other general catalogues. Here's the relevant section from the Y&T Classique.

Oh! That's what I was looking for. I get it now.
All the white paper stamps are B.
The original 1868 batch starts at 3 for the 25c stamp and Y/T just indicate carmin.
19 stamps like Zum and Mi.

Thank you for clearing this up!

Should anyone else looking for clear answers about this, find this thread, here's my Zum-Yvert Telegraph Stamp map:
Year Value Colors Zum. Y/V
1868 25c grey/carmine - 1 - 3Ba
1868 50c blue/carmine - 2 - 4Ba
1868 1 FR green/carmine - 3 - 5Ba
1868 3 FR gold/carmine - 4 - 7B
1874 3 FR brown/carmine - 5 - 6Ba
1868 20 FR pink/carmine - 6 - 8B
1877 5c black/red - 7 - 1B
1877 10c red/red - 8 - 2B
1877 25c grey/red - 9 - 3B
1877 50c blue/red - 10 - 4B
1877 1 FR green/red - 11 - 5B
1877 3 FR brown/red - 12 - 6B
1881 5c black/pink - 13 - 1A
1881 10c red/pink - 14 - 2A
1881 25c grey/pink - 15 - 3A
1881 50c blue/pink - 16 - 4A
1881 1 FR green/pink - 17 - 5A
1881 3 FR brown/pink - 18 - 6A
1881 20 FR pink/pink - 19 - 8A

Does anybody know the Scott's number equivalent?

These stamps aren't listed in Scott. Or, they aren't listed as of the 2025 Classic Specialized. I'd be shocked if they were added to the 2026.