"Why do you say this panel is upside down? Most loadcenters are designed to be mounted either way. If the feed is coming from the bottom the lugs should be on the bottom."
There was a code change some years back which outlawed any panelboard installation where the on/off wording on any breaker would appear upside down, or where the handle, when in the "on" position, would be pointing down. I forget when this took place. (Think 12-circuit Stab-Lok).
Since that time, manufacturers have reconfigured their equipment so that all breakers throw side-to-side. If no breakers are in an up-down orientation, there is nothing wrong with mounting them "upside down".
Of course, if it is a 3R enclosure, it will only go one way.