You don't really tell us anything to go on, other than the manufacturer and date. What model is it? NRA condition? Any dents in barrels? How's the wood?
In '36 Fox produced, in a side by side:
Sterlingworth
Wildfowler
Trap Double
SP
A
C
D
F
H
J
M
and X models.
Give us the model, grade, and condition, and we'll be of a bit more help.
Then you have different grades:
CE Grade
XE Grade
DE Grade
FE Grade
and Exhibition Grade.
USMC is right. Gunbroker is the place to look for similar firearm and what they sell for. A while back I was looking for a Sterlingworth from the same time period as yours and was looking at examples in slightly better condition. The price area I determined at the time was around 700. Not necessarily a scientific answer, but that’s where my analysis took me. Ultimately, I inherited my grand fathers 1929 version that looks almost exactly like yours and had it restored so I don’t have an *I paid this* for you. I can tell you what restoration costs and it’s not cheap on old doubles.