The reference for a list of suggested endorsements is AC 61-65D. I don't have an internet reference handy, but you can pick up the hardcopy at your FSDO.
The recommended endorsement for the instrument proficiency check is as follows:
Completion of an instrument proficiency check: § 61.57(d)
I certify that (First name, MI, Last name), (pilot certificate), (certificate number), has satisfactorily completed the instrument proficiency check of § 61.57(d) in a (list make and model of aircraft) on (date).
S/S [date] J. J. Jones 987654321CFI Exp. 12-31-00