How do I know if the batteries I have are rechargeable?

I have a battery pack without a particular indication. It comes from an old notebook IBM. They are marked as P/N FRU 84G6668 and P/N 84G6620. The package is composed of 3 cylindrical battery 10 diameter by 16 mm high, strange format for me. By search, I’ve found those codes, but no other information. I think they are Ni/Cd or at most Ni/MH, but I’m not sure. I have to replace them ad I cannot use a not rechargeable battery if the circuit recharges them. Reading this doesn’t help me: How to differentiate rechargeable from non-rechargeable batteries?