Technically, the semantics of the magnitude comparing operations are different for Associations, because the messages <, <=, >, and >= are defined in terms of the key only, while the = message is defined in terms of both the key and the value. This means, for example, that <= is not the "logical or" of < and =. Despite this, Association has been grouped with the magnitude classes because that is where it is traditionally implemented in the Smalltalk environment.

Both VA Smalltalk and Objectworks\Smalltalk define the = message in terms of both the key and the value. Smalltalk/V defines = in terms of the key only. Smalltalk/V does not provide the message key:value:.

Although not included in the Blue Book, this convenience method is provided by most other Smalltalk implementations.