I was looking through my M4s and noticed one of my Uticas that was different than the other two. Both the handle and latchplate were different. The handle had 6 narrow grooves and the latchplate only had a dimple instead of the SP. A bit of research revealed that it was an early version that was equipped with a Utica latchplate. Here's some pics of it.

Very nice Utica M4.  Your bayonet was made before February 1945 based on the tapered pins in the latch plate.   You are correct that Utica used their own latch plate early on for their M4 which had the dimple. Not sure when they went to the Standard Products latch plate.  

The leather grip is not a very early grip.  The first type of grips used on all the M4s were made by using alternating 2 large and one small leather washers. Your M4 leather was made by cutting the grooves.  

The first contract for the Utica M4 bayonet was  8/11/44, so your bayonet was made sometime after that date and before 2/45.  

The pic shows a CASE M4 with the early grips. The early Utica grips will look similar.

Marv