The ballpark estimate would be a range of $800 to $1,200. Lower end if it is functioning (but might need an overhaul to be accurate and crisp), and might show some age on the hands and dial. Higher end if it is keeping good time, functioning crisply and near mint / good color / patina on the dial and hands.

As you point out, we can be much more accurate if you provide photos. also, you will do well to check the timekeeping against an accurate digital clock, to see how many seconds it gains or loses in a day.

Jeff