Coated RED Scale. The best of both worlds.
I don`t wish to start a debate, but I find no advantage to an uncoated lens even in very contrasty conditions. It does not get more shadow detail or hold highlights better.
They mearly compress the smaller range they do pick up.
Decades back, I used an uncoated one, pull process E6, and printed Cibachrome without a mask. It was beautiful. The slides looked absolutely terrible and were worthless for anything else.
Look out for fog and scratches and signs of tampering. A focus that works and a diaphragm that is smooth to operate. A red scale will give beautiful old style pictures.
Stay away from cheap adapters.