Possible enhancement for basic search box

[wlpotter]

What is the feasibility of adding a selector to the basic search box that lets users choose to search all fields, the shelf mark field, or Wright's Roman Numeral entry field (and others, possibly)?

This could look similar to the search box for the Sinai Manuscripts Digital Library which lets users select the fields to search. (SMDL uses a Solr index, fyi)