The doubling commonly seen on the last two digits of the 1944 Lincoln cent was long thought to be the result of master die doubling. This determination was changed when it became apparent that the last two digits were engraved into the master die of that year, rather than punched-in. The doubling would therefore have to be the result of re-touching the last two digits.
The images above show extra serifs at the bottom of the last two digits (“44”) as well as notching at various location. As the master die transfers its design to a succession of working hubs, these faults became less distinct over time. The image above and to the right shows the gradual fading of those errant marks.