PC Lighting Question

[bededog]

I just got a used PC light fixture. There are two bulbs in it and I am not sure what Wattage they are. There is a combination of numbers and letters on the bulb and in the middle of this there is a 55. Do you think the bulbs are 55W? I would also like to know what is the difference between a 55W and a 96W bulb, other than the obvious wattage difference. Are the 96W bulbs just longer? Could I put 96W bulbs in this fixture if they will fit. Will the ballast or whatever the other parts are handle a bigger or more powerful bulb?
Thanks in advance for any help that is given.

 

[bededog]

Thanks Kip. One other quick question. What is square pin and what else is there. I just want to make sure I buy the right bulbs.