[Bindlestiff]

I did a google search for parker vent rib barrel and found some pictures, here are a few:

https://www.gunsamerica.com/98168800...L-LIVE-BIR.htm

http://ironmenarms.com/listings.php?id=756#

http://images.gunsinternational.com/...BFF785F62B.JPG

http://www.rockislandauction.com/pho...113-S-F2-L.jpg