A part of the tag is different in each version as follows:
■ The newer version of the plan tag (typesquare.js v3)
<script type="text/javascript" src="//typesquare.com/3/tsst/script/en/typesquare.js?[your plan ID]" charset="utf-8"></script>
■ The previous version of the plan tag (typesquare.js v2)
<script type="text/javascript" src="//typesquare.com/accessor/script/typesquare.js?[your plan ID]" charset="utf-8"></script>