Missing bleed valve knob - cast iron rad

Hi there

We have orginal 1930s iron rads in our house (mostly Corto). There is one small rad (6 single fins mounted against wall) in a utility room that doesn’t seem to be heating. I am wondering if it has air in it - but it appears to be missing the knob to bleed it. Can I just use needle nose pliers to turn it ? Or should I try and locate a replacement knob?

Thanks !