In a bahuvrīhi samāsa the word mukha denoting 'an actual mouth' has optionally the acute accent (udātta) on the final when preceded by a participle in ta or by that wherewith something is compared.,
Thus प्रक्षालितमुखः꣡ or प्रक्षालित꣡मुखः or प्र꣡क्षालितमुखः ॥ When the final is not acute, then Rule 6.2.110 applies which makes the first member have acute on the final optionally, and when that also does not apply, then by 6.2.1 the first member preserves its original accent, which is that of the gati 6.2.49. Thus there are three forms. So also with a word denoting comparison:- सिंहमुखः꣡ or सिंह꣡मुखः, व्याघ्रमुखः꣡ or व्याघ्र꣡मुखः ॥,