No makers name devalues the gun considerably in terms of price. Doesn't necessarily devalue it in terms of how good a gun it is ("gun for the money"), but the no name part factors in heavily when it comes to price.
The vast majority of Francottes were not sidelocks, but rather high quality sideplated boxlocks. And it should say "Francotte" somewhere on the gun. If not, one of the proofmarks would have to be the Francotte proprietary AF under a crown. Otherwise it's not a Francotte.
Something like the gun you describe, if it carried maybe the Lebeau-Courally name, or one of the other top notch Belgian makers, could easily be worth $10-15K. Maybe more. No name, even if it's the same quality, it won't be worth half that.
