An older Wratten filter designation used letters and numbers. Newer Wratten nomenclature uses numbers, sometimes followed by a letter. Hoya uses letter+number, but often shortens the designation to letter only. B+W uses a three digit number code, and Schott uses two letters + a three digit number.
Tiffen Green 1 is a Wratten #11, and their green 2 is a Wratten #13. Tiffen also makes a Green 56 and Green 58, which are the same as Wratten #56 and #58. The current Tiffen numbers 1 and 2 are probably shortened forms of Wratten letter+number designations. The Wratten #11 was also an X1, and is equivalent to the G11 or 060 filters in other systems. The Wratten #13 is also an X2, and called the 061 in other systems. Both the #11 and #13 are yellow-green.
Astrophotography books refer to the Wratten #13 as a "more efficient" version of the #11. The #11 and #13 pass the 480-580 nm spectrum, and the #11 has a filter factor of 4 and the #13 a factor of 5. I suspect that the "more efficient" comment means that the #13 has a sharper cutoff, i.e. is better at blocking unwanted wavelengths outside the passband.
The Wratten #56 passband is listed as 490-580, and the #58 as 505-560.
B&H tends to list multiple filter designations on their web site, so you might find that helpful.
Lee