Old - 1920s 0.87ct ring - whats the fair price?

[faucalt]

Hi again
Having such a perfect exp. with this forum and kind people here, I would like to ask again for help.

Relative of mine, is considering an old ring.
Unfortunately it has only a cert from a local jeweller so I have only few specs.

0,87ct
Si clarity (its eye clean)
TCA colour (which i guess translates to something like K or L)

It was made in 1920s.

Asking price is around 1,700$.

Based on this information is it possible to evaluate if the price for the ring is adequate?

pic. of the ring

 

[stone-cold11]

Get it independently appraised? Maybe with an appraiser familiar with old cuts? Could be a transition cut from the year of the ring, I think.