That is possible, and it’s good that you’re thinking about that before tuning it up! If they are thicker strings, then it could be dangerous for the harp to try tuning them up to C. It’s also possible that they are our standard strings, but just tuned down, in which case it would be safe for the harp to tune them up.
I’m not sure what the best way is to tell, unless you have calipers and you can measure the diameters of all the strings. Maybe a starting point would be to look at how many wound strings there are, and what colors they are. Is the lowest string red or clear?