What did the missing bits look like?

My two cents:
Not old as in early 1900s. Maybe 1970s, if not 1970s, then a modern remake.

I would guess that a faceted glass bead(s) hung from either side. Color matched to the glass already showing. I don't think anything hung from the bottom.

Again, only a guess.

 

Think that toggle clasp pushes it even farther forward in time. If you knew what used to be there, what would you do with the information? Agree with CC that some kind of dangles that coordinated with that golden topaz color hung off the arms & that nothing hung from the bottom.

 

I'm with the others, 70s Art Nouveau revival, maybe even early 80s.
The toggle clasp is an ancient type clasp which was used a lot in the 70s and early 80s. That is also a period with a revived interest in Art Nouveau. The clasp was hardly used in the Art Nouveau period, and I wouldn't expect it on a Bohemian style necklace like this.
You can still get Czech faceted topaz glass teardrop beads to replace the dangles, and it will look very pretty.