Actually, according to my FSDO, an AGI *can* sign off canddiates for
the Instrument written. You don't need to be a IGI. this is based on:

14 CFR 61.215 - Ground instructor privileges.

(b) A person who holds an advanced ground instructor rating is
authorized to provide:

(1) Ground training in the aeronautical knowledge areas required for
the issuance of any certificate or rating under this part;

(2) Ground training required for any flight review; and

(3) A recommendation for a knowledge test required for the issuance of
any certificate under this part.


Additionally, the FAA's Part 61 FAQ (
http://www.faa.gov/avr/afs/afs800/docs/pt61FAQ.doc ) , while holding
little or no legal authority, specifically states that an AGI with no
IGI can sign off a recommendation for an Instrument written test.

How often will it happen? Beats me...I'm a CFI and AGI, and I've never
endoresed anyone for the Instrument written. But (even without a CFII
or IGI), it appears that I could.

Cheers,

Cap