Greek Diacritics Riddle

I am transcoding into HTML a printed document from the early 1900's c.e. containing a mixture of Latin, Hebrew, Greek, Arabic, and (mostly) English.

In the rather longish (and Latinish) title are two words in Greek:

Word in Greek

and

Word in Greek

I unfortunately don't know Greek, and I can't seem to find the "accented" letters in either the "Greek and Coptic" or the "Greek Extended" Unicode ranges.

The diacritical in question seems to be what Unicode calls the "Combining Inverted Breve" (0311). I was able to achieve the above rendering (in most current browsers) by using ...

τω̑ν

and

του̑

However, in a later-published reference to this document, these "Combining Inverted Breves" have become what look like tildes — and what are apparently called (by Unicode at least) "Perispomenis"! But the Unicode "Greek Extended" range only refers to one Omega + Perispomeni combined with a "Psili" (1F66, resembling a right single quote), and another combined with a "Dasia" (1F67, resembling a left single quote).

So it appears that both the "Inverted Breves" and the "tildes" may represent something else altogether.

Anyone know what the real code points are that would make these properly encoded words?