The rules that use the vocabulary item "silver" are:

<point_type-not_ranked-checkpoint-sing>

silver

<point_type>

silver

<color>

silver

<point_type-checkpoint-sing>

silver

<air_call_sign_prefix>

silver

silver eagle

<point_type-not_ranked-sing>

silver

<air_call_sign_prefix-not_takes_digit>

silver

silver eagle

<frequency_code>

silver

<point_type-sing>

silver

<point_type-not_ranked>

silver