I look at the gun as compatible with Francotte "bottom grade" serial number range for the estimated date of manufacture. Sure looks like a Francotte, although I can't remember seeing a picture that identifies the extension rib too clearly. Is it a Greener crossbolt/extension or something else? We would also like to see a good picture of the single trigger. If it is a retrofit Miller or something similar it may add to the value. Another value consideration is "Would you like to own David Letterman's bird gun?"