Vos qui secuti estis me

Folio: 
270v
Sequence: 
9
Feast: 
Office/Mass: 
L
Genre: 
A
Position: 
B
Cantus ID: 
005502
Mode: 
1T
Differentia: 
?
Extra: 
057v
Indexing notes: 
Mode 1 is indicated, but the differentia is very faint (if it's there at all).