Welcome to the forum , mrs hooty .
I've seen the value on phones like yours (as in what folks will pay for them) go up & down , depending on the 'market' (as well as the actual condition of the unit) .
Best value , for collectors , in my opinion , is with a 100% original and functional phone (original finish too) .
There's a couple of companies that rewire these units & leave the original 'works' intact too .... I've seen this type being sold for as much as $595.00 (+all the extra shipping , etc.) .
Is yours all original & functional ?
Are you trying to establish a value for selling , just knowing , or for insurance purposes ?
You can simply type in the search term "Stromberg-Carlson oak wall phone , 1894" on your internet browser & find a bunch of info too ...
Attached photo is one of a 'rewired' Stromberg-Carlson wall phone , like yours .