Closed chamber with flat tops

Part #53005714 on the heads........These were never open chambered I am sure. If they were milled THAT much I'm sure we would probably have 3 sided ports LOL! All I know about the heads is they are 1.78-1.5 valves.
I haven't measured how deep in the hole they are yet........kinda a moot point after Moper's schooling of me.
Thanks.