I found this in the closet and I had labelled it as 'Korona View Extension' . I think it is for the 8x10 Korona.
Rail is about 215mm wide, 20mm high and approx 14 1/4 inches long.
$50 + $10 shipping CONUS. I accept Paypal if the buyer pays with a bank balance or pays the credit card fees (about 3%) and I accept USPS money orders. Check's ok if I know you.
These were usually individually matched to the camera, with a manufacturing number on the rail that matched the number on the body, so even if it is for the right model camera, there's no guarantee that it won't need to be re-fitted. On the other hand, a rail that needs to be re-fitted is better than no rail at all.