To show the product model in the popup you could edit admin\popup_product_id.php as follows:
Line 29 - change
$products_list_query = tep_db_query("select pd.products_name, p.products_id from " . TABLE_PRODUCTS . " p left join " . TABLE_PRODUCTS_DESCRIPTION . " pd on p.products_id = pd.products_id where pd.language_id = '" . (int)$languages_id . "' ORDER BY pd.products_name");
to
$products_list_query = tep_db_query("select pd.products_name, p.products_id, p.products_model from " . TABLE_PRODUCTS . " p left join " . TABLE_PRODUCTS_DESCRIPTION . " pd on p.products_id = pd.products_id where pd.language_id = '" . (int)$languages_id . "' ORDER BY pd.products_name");
After line 59
<td align="left" valign="top" class="dataTableContent"><b>Product Name</b></td>
insert
<td align="left" valign="top" class="dataTableContent"><b>Model</b></td>
After line 69
echo '<tr class="dataTableRow"><td align="left" valign="top" class="dataTableContent">' . $products_list['products_name'] . '</td>';
insert
echo '<td align="left" valign="top" class="dataTableContent">' . $products_list['products_model'] . '</td>';
If your descriptions are long you may need to change the table width (line 55 of this file) and the width of the pop-up, defined in admin/categories.php, search for
<script type="text/javascript">
function openSKUpopup(popurl){
var winpops=window.open(popurl,"","width=450,height=500,scrollbars=1,resizable=1,top=0,left=0")
}