[DCRM-L] Signature question

[Laurence Creider]

Folks,
I am cataloging Commemorationes, seu, Suffragia sanctorum Ordinis minorum 
S.P.N. Francisci .... Mexici :ex Typographia matritensi in via S. 
Dominici & Tacubae, [17--]. [24] p. ; 15 cm.

Medina  8973

The pages are unnumbered and the only leaves signed are B1 and C1.
In addition to 1 later blank leaf, conjugate with blank leaf at end the 
item consists of 
leaf [1] conjugate with leaf [12], so what appears to be [A1].[C8]
leaf [2] conjugate with [11] [A2].[C7]
leaf [3]  conjugate with 10   B1.[C6]
leaf [4] conjugate with 9    [B2].[C5]
leaf [5] conjugate with 8    C1.[C4]
leaf [6] conjugate with 7    [C2].[C3]--stiching through here.

I've looked at Gaskell's diagrams and nothing seems to fit.  The closest 
patterns are those for 12mos, esp. fig. 56.  There appear to be water 
marks on leaves B1 through [C5] or [C6], which does not make sense 
and the chainlines are vertical.  I am sure I am missing something 
obvious (my visual imagination is not good), so can somebody help?

Thanks,
Larry

Laurence S. Creider
Special Collections Librarian
New Mexico State University
Las Cruces, NM  88003
Work: 575-646-7227
Fax: 575-646-7477
lcreider at lib.nmsu.edu