GR translation: their typewriter keys chattery as their pearlies

[Mike Jing]

P79.30-34   Secretaries in woolen shawls and rubber galoshes shiver
with the winter cold being inhaled through the madhouse’s many
crevices, their typewriter keys chattery as their pearlies. Maud
Chilkes, who looks from the rear rather like Cecil Beaton’s photograph
of Margot Asquith, sits dreaming of a bun and a cup of tea.

I thought here the "pearlies" refers to teeth, but the wiki points to this:

http://en.wikipedia.org/wiki/Pearlies

which doesn't make sense to me in this context.  Am I right on this?