The way to easily tell if it's a 754 is simple - Look at the pin area of the chip you have. If you see an area that's missing pins in it's center, it's a 754 chip.
If the pin area of the chip is full of pins it's a 939 or an AM2 since there is a A64 3200+ chip for that socket too.
To tell whether it'a a 939 or an AM2 isn't too hard if you know what to look for and you'll find this info in the CPU's model name info. If the name reads as ADA3200DAA4BW or any variant with a "D" after the model name it's a 939 chip.
If it has an "I" such as ADA3200IAA4CN or any variant of a 3200+ model, it's an AM2 chip.