Most of this has been discussed in detail on the RW discord including ChameleonCir comparing the markings on the inside of the bell's and they do appear to match.

There is also always the chance that we've read either serial incorrectly but both do appear to definitely be a R3_7, however while both appear to be an 8, there is the chance that it could be a 0.

Now the main thing that's made me unsure about this is that SpaceX didn't mention that they were reflying an engine. This is unusual as you would expect there to be a big deal about "being on the way to rapid reusability".