Correct Slide for IBM?

[emmagee1917]

I have #3955066. It has a type 3. A friend bought it from an OLD gentleman in the mid 90's. He claimed his Seabee group stole it and everything not nailed down out of the LSTs arms locker the night before they landed on an island of contested real estate after being issued their " defensive armament " for the duration , a .45 M1911 and 3 loaded clips each. He claimed to have never fired it in anger , but it did give comfort 2 or 3 times. He kept it all this time , but didn't have anyone in his family to leave it to that he'd know would take care of it. It has been taken care of an looks to be almost factory new and orig. , easily in the top two of all the carbines in my collection.
The type 3 did bother me a lot , but , man , it just looked right. The lastest indications are that some of IBMs subcontractors might NEVER had upgraded to the type IV.
Chris