Correct spelling for the English word "Potance" is [pˈɒtəns], [pˈɒtəns], [p_ˈɒ_t_ə_n_s] (IPA phonetic alphabet).
The stud in a watch in which the lower pivot of the verge plays.
Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874.