October 7, 2014 USPTO Objections
USPTO Notices to File Corrected Application Papers often request capital letters to follow the figure number in multi-part figures (i.e. change FIG. 4a to FIG. 4A), basing the objection on the rule cited below.
By default, we capitalize all letters in figure labels, to avoid patent office objections. Some clients ask for us to retain lower-case lettering to match the style in the Specification; this is done at the risk of a potential Patent Office objection.
37 CFR 1.84(u)(1)
(u) Numbering of views. (1) The different views must be numbered in consecutive Arabic numerals, starting with 1, independent of the numbering of the sheets and, if possible, in the order in which they appear on the drawing sheet(s). Partial views intended to form one complete view, on one or several sheets, must be identified by the same number followed by a capital letter. View numbers must be preceded by the abbreviation “FIG.” Where only a single view is used in an application to illustrate the claimed invention, it must not be numbered and the abbreviation “FIG.” must not appear.