4/0 AL... how can I know?

I'm short on spaces in my current load center and I can either add a subpanel (quick and cheap) or replace the entire load center by a bigger one rated for 200A (more expensive but cleaner). The current load center is protected by 100A CRN fuses instead of a main breaker, so my guess is that it's old anyway. As I don't want to have to have my whole electrical service replaced, a subpanel will make a good mid term solution.
But I'd like to know how much current I can get from my service drop. The entry point itself is protected by two NRN 150A fuses, but that last upgrade probably goes back to the 70s and I don't know if the electrician back then put the biggest fuses he could. The counter is rated at 200A.
I saw a few tables that indicate that I need 4/0AL cable coming in, but how the heck am I supposed to verify what type of cable I have? I checked the exposed envelope of the cables coming in and can't read anything about their rating. Any suggestions?
Thanks, I'll summarize.
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Thanks for the details on identifying 4/0 cable, Donald. I'll check that out this evening.

Maybe the cable is 2/0 or 3/0, but I didn't find any reference on the web to help me identify it. I'd just like to know for sure what's in there because I'm curious.
I don't know if the service drop was replaced when the previous owner upgraded from fuses to breakers. If he didn't, then I must assume this is cable from the fifties so it's definitely not 4/0. And I won't consider upgrading the service drop unless my insurance company forces me to, or if I ever burn one of those 150A fuses. :)
Thanks
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On 16 Jul 2003 09:21:40 -0700, snipped-for-privacy@mail.com (Max Voltaire) wrote:

Yer not gonna get the answer you need on the Internet. Yer gonna hafta have somebody look at what you have...in person.
Call your utility company. Most will come out at no charge to look at what you have.
Or you can call an electrician...to get a free estimate.
Good luck.
Have a nice week...
Trent
Follow Joan Rivers' example --- get pre-embalmed!
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(Max Voltaire)

amp
Why would you advocate calling an electrician for a free estimate and wasting his time when the poster seems to be interested in doing it himself? Why not suggest calling an electrician and offer to pay for his advice?

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