there is only one template in the folder, buy.tpl.
Inside of it links to some buttons templates:
Code:
{if $p.appearance.added_to_cart}
{include file="customer/buttons/buy_more_list.tpl" type="input" additional_button_class="main-button"}
{else}
{include file="customer/buttons/buy_now_list.tpl" type="input" additional_button_class="main-button"}
{/if}