What you have is the later style AC system that kicks butt! The cylinder or tower you are referring to is the accumulator.

Now, to figure out if it has been converted or not. On the U-shaped pipe that exits the passenger side of the accumulator and runs to the firewall, there is a fitting that sticks up, here is the easiest way to identify the refrigerant.

If the fitting has a metal threaded cap on it, it is R-12.
If the fitting has a plastic threaded cap on it and it says max 6Nm, then it is R134A.

This system is much more efficient than the expansion valve based system used up through 1990. If your system is still R-12, FCP groton does sell a conversion kit for less than $100... it includes the oil, O-rings, new U-pipe, and accumulator plus a few other items.

I would highly recommend flushing the system if you are doing a conversion, you will also need to drain the compressor and refill it with the new oil. Finally, replace the orifice tube. Then vac it down and re-charge the system. NOTE: This is an oversimplification.

jorrell
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92 245 250K miles, IPD'd to the hilt, 06 XC70, 00 Eclipse custom Turbo setup...currently taking names and kicking reputations!