Help identifying IBM mixmaster

Hi guys, I just received a rack-grade IBM circa Oct. '43. Unshot, I am pretty pleased with it, muzzle just below a 3, overall clean metal, flat bolt, two-screw handguard. The stock is definitely a well-dinged RG M2 with only a number 7 stamped on the end of the pistol grip. Pretty sure it is walnut.

Only noticeable IBM parts are the receiver & barrel.
Lots of Inland parts including:
Trigger assembly--Inland
Bayonet mount--AI marked
Butt plate--late Inland
Adjustable sight is marked JAO, which I think is Inland
Recoil plate is w/o markings
The flat bolt is Underwood marked *U*

The parts I don't know the makers of are:
Hammer marked with an S followed with an O or C or G that is worn
Operating rod marked PI in a circle
Front sight marked N
Mag release marked M with either a CO or OO or CC above it
The flip safety is hard to describe, it looks like a circled II with "tails" coming from the top left and bottom right of the characters
The 2-screw handguard is marked RSG; could that be made by Rock-ola for Saginaw?
I don't have the tools or the knowledge to strip the bolt or trigger assembly further at this time.
It kinda looks like overall I got an IBM/Inland mix.
I am still pretty new to the wonderful world of M1 Carbines and this is my second carbine following a 12/43ish Standard Products I bought two months ago on Gunbroker.com. I really appreciate those who take the time to help me better understand my new addition.

You have more Inland parts then you realize. The slide and the front sight would be correct for Inland. The hammer is most likely SG for Saginaw Steering Gear. The magazine catch is a replacement made by Commercial Controls. The hand guard was made for Saginaw by Robert Irwin. The safety is a post war replacement. hth

Below are two step by step disassemble guides for the bolt and trigger housing.

http://www.alpharubicon.com/leo/carbinetriggergroup.htm

http://www.alpharubicon.com/leo/sergercarbinebolt.htm

Recommend buying a bolt tool and trigger spring tool to make it easier, but it can be done without them. (Bolt tool is definitely worth the money IMO)

Thank you both for your help and information. Looks like I need to buy an Inland in the hopes of getting some IBM parts!

I had not seen the alpharubicon link before. This really explains the process well and will be a big help.

Bruce, is the Commercial Control for my mag catch the same Commercial Controls that National Postal Meter became?

I use a fairly large old Tupperware container with high sides and flat bottom when I take these assemblies apart to catch springs and small parts. It's good to use for assembly as well to help from losing small parts and springs.

They tend to go into another dimension when they get away from you guaranteeing cuss words you probably seldom use. :bitch:

Actually it is the other way around. A few days before the end of the carbine contract,NPM renamed itself Commercial Control Corporation.