Tom pointed out something I didn’t know. Some M-38s have patches along the top of the rear of the M-38 body over both rear vertical seams. This was a technical recommendation was the result of a problem caused by the weight of arctic tops, leading to the separation of the rear body seams.
Below are two unpatched examples:

This example shows the crude patch example:
This tub looks to have been patched on both sides:

































