You need to create an event view with the asset ID as relationship.
Then, add the field Asset serial number and select the right relationship, which should be below or above the Label setting.
I don't think this is the best option. It could be really performance consuming.
First you need to create an event field view with event type and asset ID (the asset ID should be excluded from display). Go into the view folder, open theme, copy the views-view-unformatted.tpl.php file and paste it into you theme folder with the other template files (sites/all/theme/YOURTHEME/template).
In the third column, click on theme and look for the style output (views-view-unformatted.tpl.php). There will be many of this. Use the more specific for that view (usually the last one), something like views-view-unformatted--event--page_1.tpl.php.
Rename the file you copied in your template. Create an asset field view with the serial number and the node ID as contextual filters.
This is how a views-view-unformatted.tpl.php file looks like.
<?php if (!empty($title)): ?>
<h3><?php print $title; ?></h3>
<?php endif; ?>
<?php foreach ($rows as $id => $row): ?>
<div class="<?php print $classes_array[$id]; ?>">
<?php print $row; ?>
</div>
<?php endforeach; ?>
You should modify it in this way
<?php if (!empty($title)): ?>
<h3><?php print $title; ?></h3>
<?php endif; ?>
<?php foreach ($rows as $id => $row): ?>
<div class="<?php print $classes_array[$id]; ?>">
<?php print $row;
print views_embed_view('ASSET_VIEW', 'page_', $view->result[$id]->YOUR_FIELD);
?>
</div>
<?php endforeach; ?>
Test it.
print views_embed_view('ASSET_VIEW', 'page_', $view->result[$id]->YOUR_FIELD);
will print the asset view. $view->result[$id]->YOUR_FIELD
will print the asset ID from the event view.