Hello,
I have this gist, which is a working example of how to add a field to your product add/edit template (product-edit.php) and then have the output display on the product page.
It looks as if you have already done at least part of this process; however, if you take YOUR code,, and compare it to this gist, do you see anything different? Mine is just a simple field for the vendor to add the text new or used, rather than a select box:
https://gist.github.com/fervous/ce8059e2144f05b813c5932fbd1d3c6d
