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