Hi, do I need to apply thermal compound to a Pentium II CPU heatsink?

I have a few Pentium II's that I bought used, and none of them have thermal compound between the CPU and the heatsink.

Unlike with the Pentium III, the Pentium II has a metal cover over the actual CPU, so that heatsink is actually touching another flat metal plate.

I would imagine that adding thermal compound would not hurt, but just not sure if it is needed or if it actually helps on a Pentium II.

Thanks.