Perry's Index to the Aesopica
Perry reserves 420 for a long joke about an adulterer which Perry found
in the Byzantine mss. Laur. 57.30 and Athen. 1201.
You can find a compilation of Perry's index to the Aesopica in the gigantic appendix to his
edition of Babrius and Phaedrus for the Loeb Classical Library
(Harvard University Press: Cambridge, 1965). This book is an absolute must for anyone interested
in the Aesopic fable tradition. Invaluable.