What is the source for Heirloom weapon

[Suzaku]

No I'm not talking about the one I refuse acknowledge (Adventure's Armory).

[Enevhar Aldarion]

If you are talking about what book it is printed in, that is the only place it has appeared.

[Suzaku]

So where did the original come from then?

[Enevhar Aldarion]

The same book. The original version of the trait was in the first printing of the book and the errata version of the trait replaced the original when they did the second printing of the book.