Your best source of value information is the Blue Book of Gun Values.
It uses the much more accurate % of Finish system versus the antiquated and inaccurate NRA system. Still, local price variations hold sway.
This is an out of production foreign gun. Not to say this is bad, you just have to understand the deal- I own and love my Model 3000 !
A big factor is the gauge. 20 gge and .410 bores can add 25% to the value.
There are several Falconet models, the "S", the field, the skeet, international skeet, std trap, international trap.
Most likely it is "The Field" model, and in pristine 100% condition it would bring maybe $600 at full gun shop retail.
I can not recommend one single book more highly than the Blue Book of Gun Values
Hell, almost any O/U is worth $600.
Doc @ M&A Parts