meter size by visual?

Learned during training that the round meter with no square box behind was 60 amp, the square box was 100 and the rectangle was 150-300.

I have been getting into an older area of tow and find homes with the round meter/ base and the home has been rewired with vinyl copper wire and a 100-125 amp box with appropriate service entrance.

How does one know if meter is correct as i was told by a utility service guy the meter can be changed out still in the round box to meet the new requirements/service

Good question. I have wondered the same thing.

The type/shape of the meter base (round, square or rectangular) is merely an “indication” of the service capacity. Generally speaking, the maximum wire size that can be used in a round base will accommodate up to a 60 amp capacity, up to 125 amps in a square base, and so on, but this is not definitive and the final determination will likely be determined by your utility company and/or AHJ.

In the Los Angeles area, it’s quite common to find 100 or 125 amp upgrades on a round meter base (with a 15 amp meter) that has been approved and permitted by Building and Safety.

There are some of the same answers here

I recently had a house with a 200 amp rated meter installed in a round base. Actually two bases with one closed off. House had 125 amp service, no main, not a split buss and a full panel box.

Good deal, i didnt call it out as it had a recent city elec insp sticker. Thanks for the clarification