[DCRM-L] long 12mo or 18mo?

[Deborah J. Leslie]

I see that the question has been answered admirably on ExLibris. Students of my course at Rare Book School may remember the two "extra credit" format identifications were of a long 24mo and an 18mo. The easiest way to tell them apart is by proportion. A long 24mo will be roughly 2-1, while an 18mo is  closer to 5-3. The Gaskell figures of different imposition types are helpful that way.  

Deborah J. Leslie | Folger Shakespeare Library | djleslie at folger.edu | 202.675-0369 | 201 East Capitol St., SE, Washington, DC 20003 | www. folger.edu

-----Original Message-----
From: dcrm-l-bounces at lib.byu.edu [mailto:dcrm-l-bounces at lib.byu.edu] On Behalf Of silvanan at mptek.net
Sent: Monday, 16 November 2015 17:47
To: DCRM-L
Cc: EXLIBRIS
Subject: [DCRM-L] long 12mo or 18mo?

Hello there,
I was hoping someone could help me determine if my book format is long 12mo or 18mo. 
La liturgie, ou, Formulaire des prieres publiques ...
A Dublin : Chez G. Colles, R. Moncrieffe, C. Jenkin, & G. Hallhead, MDCCLXXII [1777] A-2C in alternating 12s and 6s, vertical chain-lines, Can't really make out any watermarks.
approx. 13.5 x 8.5 cm
Most ref sources and records describe it as 12mo.

Any help would be appreciated.
Thanks,
Silvana