That's not how you define options inside a select in angularjs
Please have a look at: http://docs.angularjs.org/api/ng/directive/select.
That's how your code should look like:
<select ng-model="filtrs.model"
ng-change="filtered()"
ng-options="inventory.model as inventory.model for inventory in inventories">
<option value="">Model</option>
</select>
<!--filter inventory Manufacturer-->
<select ng-model="filtrs.manufacturer"
ng-change="filtered()"
ng-options="inventory.manufacturer as inventory.manufacturer for inventory in inventories">
<option value="">Manufacturer</option>
</select>
Once, you've changed your code, let me know if you still have issues.