When an electric meter is advertised as having different models for CL 20/100/200/320. What does each number mean? Is it current measuring capability?

 

From an article on testing meters here it looks like it is the MAX ampere rating also referred to as CLASS.

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1. 
   [*]Each meter shall have the following information legibly marked on the front of the nameplate or register:

(a) Manufacturers’ name or trademark, type designation, and serial number.
(b) Voltage rating.
(c) Test amperes (TA).
(d) Maximum amperes (CL) {meter class}.
(e) Watt-hour or disk constant (Kh) {expressed as watt-hours per revolution}.
(f) Register ratio (Rr) and multiplier (if 10 or larger).
(g) Frequency rating (Hz).
(h) Number of meter stator(s) or elements (polyphase).
(i) Ratio or rating of auxiliary devices.