Depending on the relationship the servicing dealer, and the phase of the moon, and I guess any current trends of failures Ma Mopar might or might not require any replaced item to be returned for inspection.

At 31-63436 usually there might be a request to hold the parts for inspection by who ever the current rep was out of Natick, usually low man on the totem pole, gotta break em in somewhere ... after he would glance in the box it would be "dispose of locally".

That was likely the case with this block, and instead of going to scrap, an enterprising mechanic (probably the one who did the replacement) kept it.