I noticed that too comparing mine. Definitely agree that no stock brings the value down a bit.So, the Ducktown stamped ones bring less money then the SWD ones.
If you had the stock for your carbine length gun, You would have a $750 to $1000 gun. I just sold a none function SWD one with stock for $750 and the reason I say yours is on the low end too is because I can see it's missing parts already as you can see in the yellow circle.
I'd say right now, in the condition it is in, w/o stock- $500-$600. Lucky spare parts are readily available and even the stocks or reproduction ones can be found for a few $100...
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Luckily Cobray is still in business and at least selling parts.
Semi-Auto Parts
cobray.com