Including your MCU, particularly if it's using masked ROM.

It's apparently not impossible or even grossly impractical to relabel parts. A fellow went to jail back in the '70's because he did that with components, marking them with joint army-navy part numbers that were inappropriate. The function was the same but the testing was not adequate.

More recently, I've been approached about building a device that verifies the package contains the device its external markings suggest. This implies that people are falsely relabelling components in order to sell them on the open market.

A business that sells surplus or "new-old-stock" devices for repair/replacement would be pressed to ensure it is selling what it claims and not some unrelated but mislabelled part.

RE