I used to have one from the early 1960's. It had a circular steel mount attached for an M14icon type bipod, which was locked on manually (by hand). The barrel was sold in Connecticut to a Colt collector.

I sent the bipod, years ago, to a guy doing an article along with some very early parts which were for sale. He paid me for the parts but never returned the bipod.

Over the years he avoided my calls and ignored my conversations with his employees. He will never get another thing from me, not even a conversation. He can rot in he11.