Play-Mastermind.com

I sold some pc3200 memory to someone and they said it didn’t fit their system. The memory used to be installed in a desktop but when I went over there I saw that they had tried to install it into a server that already had pc3200 memory in it. I checked the memory I had with the memory that was already installed, and they were off by like only 1 pin, and so that’s why the memory wouldn’t fit in. What kind of memory did he have? How many different ways can pc3200 memory differ from each other, physically?