Trigger Housing Picture from the auction
https://www.milsurps.com/images/impo...9/sl1600-9.jpg
Common to see Ordnance Flaming Bomb on early S'G' trigger housings.
I believe-
IP had the complete circle tooling hole. And started out making the Type II housings that still had the Narrow rear magwall, like the Type I housings others had previously made.
Saginaw took over the Grand Rapids operations and finished up any housings IP had started.
If these were far enough along with the rear bevel cut, S'G' finished it as a Type II, BUT had the still narrow rear mag wall and NO front bevel.
If the left over IP housings didn't have the rear bevel work done, S'G' made them in the Type III style, BUT again could be found with the narrow rear mag wall. After using up any IP leftovers S'G' made just the NORMAL Type III housings...... with NO bevels and Wide Mag wall.
This is why you see so few S'G' Type II Housings
S'G' transitioned to the Dimpled tooling hole..... the later style hole (but not the last style which was no hole or just a Dimple and No hole).
This one pictured has to of been started by IP.... Noting the narrow mag wall.
Then finished by S'G'. These seem to show up very late 1,7 mil - early 1,8 mil range just after the take over by S'G', often found in the split IP/S'G' serial number block.
In Short: I believe S'G' marked Type II housings you find with a Narrow Mag wall were started by IP and completed by S'G'.
Here's a link to a similar example:
My Saginaw S - The Carbine Collector's Club