The Howard Baldwin keys had “pulley” keys. “Pulley” is a strange term which basically means you can pull on the key and it will have some front to back play. The result is an uneven key line at the key slip, and the slop in the action will be evident to the pianist.
I chose to repair the condition with veneer inlays at the rear of the key hole. The job took a couple of hours, and I judge the result to be excellent. The photos below show a new, properly round hole. The veneer inlays happen to be walnut, but for 6 cubic mm of material, any hardwood would do. The walnut was just handy in the wood rack.