1) The most common chipset used in Pentium-II machines is the Intel 440BX. It is also relatively common in slower P-IIIs, and is approximately identical to the 440MX (a one-chip version aimed at laptops).
2) The 440BX has the interesting feature of only being able to address up to 128MBit density RAM. This is a relatively widely known issue.
3) Simple maths suggests that if you have a 128MB DIMM with 4 chips on it, they are likely to be 256MBit parts.
4) Marking said DIMMs as being suitable for Pentium-IIs is therefore really indescribably stupid, you wankwits. Please fuck off and die in a great big chemical fire before I get back there to beat you.
It's true that you learn something new every day. Yesterday I discovered that playdough is electrically conductive. I also discovered that RAM becomes unhappy if all of its pins are joined together with electrically conductive material.