OK - firstly and appreciating that you have said themes are not your area Mark but for the sake of anyone else who comes across this thread, this is NOT a Moodle1.9 theme which has not been modified a lot! 1.9 themes do not work in Moodle2 or 3 without a complete rewrite and you said above that you are using Moodle 2.9.7. They work in a completely different way and although it would be possible to recreate the look and feel of an old theme, it certainly cannot be done without that major rewrite.
I would take a guess then, that someone may well have copied that old theme across into your new site, but it isn't being recognised as such by your Moodle site and that you are actually using Clean (the default theme). You can check this by going to Site Administration -> Appearance -> Theme Selector and seeing what theme is listed there as the default theme.
Richard