[gb2world]

yes - the loop must also be in the product.tpl - to debug, you can add something that writes out the variables inside the loop to make sure it is working and that the variables are as you expect.

{section name=field loop=$extra_fields}
<b>field</b>: {$extra_fields[field].field}<br />
<b>value</b>: {$extra_fields[field].field_value}<br />
{if $extra_fields[field].field eq "ship_by_mail" && $extra_fields[field].field_value ne ""}
{assign var="ship_by_mail" value=$extra_fields[field].field_value}
<b>Ship By Mail:</b> {$ship_by_mail}<br />
{/if}
{/section}