The Winchester M1 Carbine receiver was different from other producers, such as the Inland Division of GM. The operating slide guide and spring were contained in a tube that fitted in a trough in the bottom right side of the receiver. By contrast, the Inland Division receiver eliminated the trough and tube by making them part of the forging. A simple bored hole replaced the tube to hold the spring and guide. Interestingly, the original wooden M1 Carbine stock was replaced by a hand carved Vietnamese replacement.
The M1 carbine story is a testament to American ingenuity and design, when you consider that of all the companies (ten in all?) that made M1 carbines during WW2, only one (Winchester) was an established gun maker.