The Project Gutenberg FAQ - C-20

C.20. I have a text that I know was based on a pre-1923 book, but I don't have the title page. Can I submit it to PG?

Unfortunately, no.

What you "know" isn't proof that we could take into court if we were challenged about it in 20 years, and the whole problem of "new copyright" [C.17] makes it effectively impossible to tell for sure what is and isn't copyrighted anyway, without reliable evidence like the title page.

You need to find a matching paper edition for proof. See the FAQ "I've found an eligible text elsewhere on the Net, but it's not in the PG archives. Can I just submit it to PG?" [V.62]