Great link CD_Yow. Thanks for sharing!

Lap belt was discontinued (IIRC) after Sioux city crash where several infants were crushed by adults in Y flipping forward. Airplane crashed are not a regular occurrence. Lap belts are very effective for turbulence and seats don't flip forward in C - so in your case a lap belt was clearly preferable over none.

No, I'm not sure if they were ever used on U.S. aircraft. In the Sioux City accident, lap babies were held to the floor by their parents per United's prepared emergency procedures.